Motivation and emotion/Book/2014/Self-injury motivation

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Self-injury motivation:
What motivates self-injurious behaviours?


Self-Injury - a coping mechanism for psychological distress

Overview[edit | edit source]

Self-injury is a commonly misunderstood, maladaptive coping mechanism that a surprising number of adolescents and young adults use to cope with psychological distress. Most of us probably know someone who has self-injured at some point in their lives, though we may not realise it. Self-injury can sometimes indicate underlying mood disorders, or progress to suicidal thoughts and behaviours. But it is also present in the absence of any mood disorder or suicidal thoughts. In any case, it is an indication of distress that should always be taken seriously. This chapter introduces self-injury, discusses the motivation behind this behaviour, and presents treatment and recovery options. You will come away with a holistic understanding of self-injury and the motivations behind it.

Definition[edit | edit source]

Case Study: Introducing Cindy

Cindy, 14, began self-injuring when she was 11. She used tools such as paperclips, pens and her fingernails to scratch the skin on her arms, resulting in multiple scars. Self-injury is something Cindy did in private, and on the outside she seemed like a calm, well-groomed individual with coherent thought processes (Askew & Byrne, 2009).

Self-injury is the act of intentionally causing harm to one's own body without suicidal intent (Polk & Liss, 2007; p. 568). It is also referred to as self-harm or non suicidal self-injury. Self-injurious behaviours include scratching, cutting, hitting, and burning one's skin (Nock, Prinstein, & Sterba, 2009). There are many myths which circulate about self-injury, including that it represents a suicide attempt. However, this behaviour has been demonstrated to be distinct from attempted suicide, in that it does not involve the intent to cause one’s own death (Posner, Brodsky, Yershova, Buchanan, & Mann, 2014). Despite this, it can still cause accidental death, and some individuals do present with both self-injury and suicidal thoughts and attempts.

Historical and cultural context[edit | edit source]

Historically, different cultural groups have delved in practices which could be seen as forms of self-injurious behaviour. Across many cultures, tattooing and body piercing have been a popular practice, however these behaviours are distinct in that they are culturally-sanctioned. Self-injury, on the other hand, is a deviant behaviour. It is considered to be outside of the realms of what is 'normal', as it is motivated by personal distress rather than cultural norms.

The first recognised attempt by a member of the scientific community to describe self-injury was by the psychiatrist Dr Karl Menninger. In his 1938 book, Man Against Himself, Menninger used psychoanalytical theory to label self-destructive behaviours, including self-injury, as a form of gradual suicide motivated by the unconscious. This view conceptualises self-injurious behaviour as a coping mechanism used as an alternative to suicide (Posner et al., 2014). Over time, several myths have developed surrounding self-injury, due to a general lack of knowledge. These include self-injury being the same as a suicide attempt, and being a behaviour practiced solely for attention. Both of these ideas are unsubstantiated (Klonsky & Lewis, 2014). Unfortunately, these myths present obstacles to understanding self-injury, which is poorly understood even among health professionals (Stone & Sias, 2003).

Within the last 15 years, the depiction and discussion of self-injury in music, movies and the media has markedly increased. News articles mentioning self-injury, for instance, have increased from just 1 between 1966 and 1970 to 1,750 between 2001 and 2005 (Purlington & Whitlock, 2010). It is unclear why this increase has occurred, although it has been suggested to be both a reflection of and a contributor to the increasing presentation of self-harm in hospital settings. The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5; American Psychiatric Association, 2013) has newly listed non-suicidal self-injury as a condition for future research, indicating that it presents a significant public health issue.

Prevalence[edit | edit source]

The prevalence of self-injurious behaviour in the general population is difficult to verify. Self-injury can be a secretive behaviour which is intentionally concealed from others (Nock, Prinstein, & Sterba, 2009). Furthermore, it can be quite superficial, and may not require medical attention (Nock et al., 2009). Thus, hospitalisation records do not account for those individuals who have never needed or sought medical help. There is some evidence that the incidence of self-injury, based on hospitalisation rates, is increasing (Muehlenkamp & Gutierrez, 2004). However, suicide attempts and self-injury are often grouped together under the category of 'self-harm' in hospital settings. This is partially due to the difficulty in ascertaining whether an individual was acting with or without suicidal intent. It is also difficult to tell whether increased hospitalisation rates are due to an actual increase in prevalence, or an increase in individuals seeking help for self-injurious behaviours.

Population surveys and study group statistics may provide a more accurate measure of prevalence. A 2006 study randomly surveyed 12,006 Australian households by phone and found that 1.1% of their sample reported self-injurious behaviours within the last 4 weeks, with an overall lifetime prevalence of 8.1% (Martin et al., 2010). Cutting was the most common method reported. Other studies have estimated the lifetime prevalence to be higher, at 17% (Stone & Sias, 2003). Self-injury typically appears to begin in early adolescence, and continue throughout adolescence, sometimes into young adulthood (APA, 2013). Reports of sex differences vary, although there is a general consensus that in adolescent populations, more females present with self-injury, but in young adult populations there are no significant differences (Bresin & Gordon, 2013).

Self-injury can also be experienced by individuals suffering from depressive or dissociative disorders, and personality disorders such as Borderline Personality Disorder (BPD; Polk & Liss, 2007). Much of the research on self-injury has focused on BPD and Post Traumatic Stress Disorder (PTSD), with comparatively few studies focusing on non-psychiatric populations (Chapman et al., 2006). Self-injury can present in individuals with no history of any of the aforementioned diagnoses (Chapman et al., 2006). Thus, it appears to be a behaviour distinct from, and not defined by, any particular disorder. The high prevalence of self-injury illustrates the necessity of understanding the motivation behind this behaviour, in order to develop and provide effective long-term treatment.

What motivates self-injurious behaviour?[edit | edit source]

If the motivation behind self-injury is not to cause death, what function does it serve? Self-injury can appear perplexing to those who have never experienced it, as it seems counter-intuitive. The motivation behind self-injurious behaviours appears to be related to two overlapping facets – the antecedent events or risk factors; and the functions which self-injury serves for the individual.

Risk factors[edit | edit source]

Case Study: Cindy's Past

Cindy had been emotionally and physically abused by her father, and as a result experienced recurring thoughts of past abuse which were very distressing. She was also neglected by both of her parents throughout her childhood. Cindy was removed from her family by child protective services when she was 13, and placed in a foster home (Askew & Byrne, 2009).

Many individuals who self-injure, though by no means all, have experienced distressing and/or traumatising events in their past. Childhood trauma has been found to be a significant risk factor; childhood sexual abuse and childhood physical abuse are strongly predictive of future engagement in self-injury (Polk & Liss, 2007). Maltreatment or neglect in childhood is also common among university students who self-injure (Gratz, 2006). These environmental events can have a lasting effect on emotional regulation; a history of trauma may contribute to problems such as Alexithymia (Zlotnick, Mattia, & Zimmerman, 2001). Alexithymia, defined as difficulty identifying, expressing and regulating emotions, is also related to the development of self-injury (Polk & Liss, 2007). Whilst Alexithymia may be present where there is no history of childhood trauma, it appears to moderate the relationship between traumatic experiences and self-injury, such that individuals who have experienced trauma are more likely to self-injure if they have difficulty with emotional regulation and expression (Paivio & McCulloch, 2004).

Functions[edit | edit source]

Self-injury is a coping mechanism for psychological distress, a state which develops as a result of difficulty adapting to stress (Walsh, 2006). Even animals, such as Rhesus Macaques, have been observed self-injuring in response to stressful situations such as moving to new housing (Davenport et al., 2008). Through studying and interviewing human self-injurers, this behaviour appears to serve several specific functions; namely to regulate emotions, punish oneself, or gain a sense of control over or distract one from thoughts or experiences. Interestingly, the majority of participants in major studies have indicated more than one factor motivates them to self-injure. Polk and Liss found that 96% of respondents expressed more than one distinct function of self-injury, for instance relief from emotional states as well as wanting to punish oneself and gain control (2009).

Commonly reported functions that self-injurious behaviours serve for individuals

Emotional regulation[edit | edit source]

The role of self-injury as an emotional regulation tool is likely related to certain brain regions, such as the right ventral prefrontal cortex, being active during both the experience of physical pain and the experience of emotional pain (Bresin & Gordon, 2013). However, further research needs to be conducted to learn more about the brain activation correlates of self-injury.

The Experiential Avoidance Model[edit | edit source]

Case Study: Using self-injury to avoid painful thoughts

Cindy would self-injure when thinking about or talking about her past experiences became overwhelming. When she experienced an intrusive, painful memory or when talking about a painful experience become emotionally overstimulating, she was motivated to self-injure in order to experienced a sense of relief from those feelings (Askew & Byrne, 2009).

First of all, self-injury is described by some as a way to release, or decrease, negative emotions such as sadness, depression, anger, or loneliness (Laye-Gindhu & Schonert-Reichl, 2005). The release of emotions is the most commonly reported function of self-injury (Polk & Liss, 2009). This function of self-injury can be conceptualised as experiential avoidance, which is the use of a behaviour or group of behaviours to achieve short term avoidance of internal events such as emotions, thoughts, and memories. As one young person describes, "It helps relocate pain from emotional to physical" (Polk & Liss, 2009, p. 236). Self-injury allows the avoidance of negative affective states by providing a physical outlet to release emotional energy (Chapman, Gratz, & Brown, 2006). Experiential avoidance behaviours are negatively reinforced, in that they are perpetuated and repeated due to their ability to allow an individual to avoid internal events. For instance, an individual may be experiencing intense anxiety, which s/he needs a way of alleviating. At some point, they attempt self-injury, which lessens their anxiety. Thus, in the future, they will be more likely to use self-injury to alleviate anxiety.

Relieve dissociative or numb emotional states[edit | edit source]

Another commonly reported function of self-injury is to experience an increase in emotions, in cases where the individual feels numb or is experiencing dissociation[factual?]. In this case, self-injury is practiced in order to alleviate dissociative or emotionally numb states[factual?].

Similar to experiential avoidance being perpetuated by negative reinforcement, self-injury to increase or add an emotional state is perpetuated by positive reinforcement, or the addition of a reward which then increases the likelihood of that behaviour reoccurring.

Punishment[edit | edit source]

Related to emotional regulation functions is self-punishment, another commonly reported function of self-injury. Polk and Liss (2009) reported 10% of their sample included self-punishment as a reason they self-injured.

"I hate who I am. I hate who I was. I hate what I am becoming. If I can work to kill that, even if only to hurt it, I will accomplish my goal. I feel deserving of punishment for my wrongdoings and if that punishment doesn't come from anywhere else, it will come from me." (Polk & Liss, 2009, p.237)

Distraction[edit | edit source]

The use of self-injury as a tool to distracting oneself from aversive thoughts and memories is sometimes reported; for instance in Polk & Liss' 2009 study, distraction was reported by 6% of participants. Distraction, a type of attentional deployment, is an emotional regulation strategy individuals sometimes employ when experiences or stimuli, either internal or external, are experienced as overwhelming (Bebko et al., 2014). Considering the intense subjective experiences of some individuals prior to self-injury, it makes intuitive sense to enact a behaviour which would provide some relief, however temporary. Prior to self-injuring, one individual reported feeling "desperation, out of options" (Kakhnovets et al., 2010).

Cognitive regulation[edit | edit source]

Although emotional regulation functions are the most commonly reported across studies, cognitive regulation functions are also reported by many. Use of self-injury as a way to regulate and slow down intrusive thoughts and memories and well as provide distraction from unpleasant thoughts and memories are common[factual?]. It is clear that cognitive regulation is related to emotional regulation, in that intrusive or unpleasant thoughts are likely to co-occur, precede or follow the experience of unpleasant emotions.

Self-control[edit | edit source]

Self-determination theory

Surprisingly, individuals report self-injury [missing something?] allows them to experience a sense of control over their thoughts and behaviours, which can be conceptualised as self-control (Nock et al., 2009). Self-control is the subjective sense of control over one's own thoughts and behaviours in response to environmental demands[factual?]. In the case of individuals who have experienced childhood trauma, self-injury may be a mechanism to experience control over high levels of arousal which during past traumatic experiences they were unable to exercise (van der Kolk, Perry, & Herman, 1991)[grammar?][Rewrite to improve clarity]. A sense of achievement and self-efficacy can result from being able to employ a tactic (in this case self-injury) to achieve a desired outcome (in this case decreasing arousal). It can be seen that this function could be maintained by positive reinforcement, as this sense of self-control is likely to be desirable, and thus will be more likely to be repeated in the future.

Self-injury used as a means to experience self-control seems to be conceptually related to one's locus of control, which refers to the extent one believes they are in control of their life. Self-injurious behaviour seems to reflect an internal locus of control, in that the individual feels able to control internal events through self-injury, without external help.

Self-determination theory (SDT) posits three basic needs that all individuals innately require: autonomy, relatedness, and competence (Wichmann, 2011). An individual who is experiencing psychological distress could feel a lack of control over their thoughts and emotions. Autonomy, the extent to which an individual feels they are able to effect their decisions and life direction, could be lacking in individuals who have experienced trauma or neglect in childhood. Certainly, viewing oneself as helpless is common in individuals who experienced childhood trauma (Cook, 2005). Thus, self-injury can be seen as a means to exercise autonomy, in order to gain a sense of control. This need for autonomy can be utilised in treatment, by teaching other, healthier means of gaining a sense of autonomy.

Illustration of self-injury as a coping mechanism, to temporarily relieve psychological distress.

Biological mechanisms[edit | edit source]

Biologically, the act of experiencing pain eventually leads to the release of endorphins and other natural opiates, and also can set up autonomic nervous system responses such as increased heart rate (Bresin & Gordon, 2013). Interestingly, individuals who self-injure may have low levels of endogenous opioids in comparison with others, and the act of self-injury, through ANS responses, increases levels of endogenous opioids, leading to a change in emotional and cognitive states (Bresin & Gordon, 2013). It may then be questioned whether self-injury is pleasurable for some individuals, and indeed it can be in some cases; however, pleasure is not a common function (Victor, Glenn, & Klonsky, 2012). The view of self-injury as a pleasurable and addictive behaviour has been explored by recent research, but models of affect regulation have proven to fit better than addiction models (Victor et al., 2012). The pain itself is not what is being sought; it is the addition of an emotional experience.

Treatment and recovery[edit | edit source]

Case Study: Cindy's Recovery

Cindy attended both individual and group therapy for 6 months. Over time, she began to open up and talk more about her past, and at times talking about her past triggered her to self-injure. Her self-injury continued unchanged for 4 months, before it began to lessen. Through re-experiencing her memories, exploring how her past has effected her current mental state, and being encouraged to engage in alternative coping mechanisms, her self-injury stopped completely. She now uses other, healthier coping mechanisms to deal with intrusive thoughts (Askew & Byrne, 2009).

Recovery can be a difficult process, but it is achievable

All of the aforementioned functions of self-injury indicate it is used as a way to cope with and temporarily alleviate internal events. But while self-injury can be effective for these purposes, it is a potentially dangerous and short-term solution. Particularly of issue is that self-injury becomes increasingly automatic the more it is employed (Chapman et al., 2006) through reinforcement. Thus, early intervention is important to recovery.

There is evidence to suggest that less than one third of self-injurers seek professional help, but a majority do confide in others (Martin et al., 2006). This highlights the need for a general understanding of self-injurious behaviours in the community, and knowledge of how to help those who self-injure. First and foremost, individuals engaging in self-injury should be encouraged to seek help. Secondly, learning healthy behaviours which can provide a physical or emotional release can help individuals to gradually replace self-injury with non-harmful activities (Klonsky & Lewis, 2014).

What is key to recovery is the individual's recognition of their self-injurious behaviour as a problem, and a willingness to change this behaviour. Cognitive Behavioural Therapy may help where individuals refuse to accept that self-injury is a poor method of coping, as it is a well-supported therapy for changing distorted thoughts and also in treating comorbid depression and anxiety (Askew & Byrne, 2009). Training in effective problem-solving has also been found to aid recovery, as it aides the conscious recognition of self-injury and self-directed development of other coping mechanisms (Askew & Byrne, 2009). It is always important to seek counselling in order to ensure safety and develop an appropriate treatment plan for self-injury.

How can I help?

If someone opens up to you about their self-injury, it is important to listen, be non-judgemental, and to encourage them to seek help. See Headspace's article 'how can I help?', for more information.

Prevention[edit | edit source]

As discovering the motivations behind self-injury is still a work in progress, very little research has been conducted as to the ways we can prevent self-injury from occurring in the first place. Much research so far, though, does indicate that self-injury is a coping mechanism. Thus, the preemptive development of alternate, healthy coping mechanisms may be beneficial. The behaviours in Table 1 have been shown to be effective coping mechanisms for dealing with psychological distress[factual?]. It is important to teach and encourage these behaviours in children and teenagers, but also at any age, in order to maintain emotional health.

Calling a helpline to speak with a counsellor can be helpful

Table 1.

Caption Goes Here

Healthy Coping Mechanisms
Talk to a friend Discuss your thoughts and problems with a trusted friend
Talk to a professional Make an appointment with a counsellor or psychologist, or call a helpline to talk to a phone counsellor
Exercise Go for a walk or run to release pent up emotions, or just to feel better
Write it down Sometimes getting your thoughts out onto paper can provide an emotional release
Practice relaxation Download a meditation or mindfulness app or join a class to learn how to relax your body and mind

Further your understanding[edit | edit source]

Despite reading all about self-injury, it can be a difficult behaviour to understand by those who have not experienced it. The act of self-injury may seem foreign and scary, but it is important to understand, given it effects such a large proportion of people. The following video, made by Headspace, is a dramatised piece based on real interviews with an adolescent girl who experienced self-injury. It includes the self-injurers perspective, as well as her support network's perspective. You are encouraged to watch it in order to develop your understanding.

Watch a video about the lived experience of self-injury, treatment, and gradual recovery

Headspace

The following Insight episode is a group discussion which will further your understanding of self-injury and give you 'bigger picture' insight. You will hear from self-injurers, health professionals, teachers, and principals about the overall incidence of self-injury and the problem it presents.

Insight: Scars

Insight

Conclusion[edit | edit source]

The key points to take away from this chapter are:

  • Self-injury is a relatively common, maladaptive coping mechanism, particularly in adolescents and young people
  • It may or may not be related to underlying disorders or suicidal ideation
  • Self-injury is a serious action which communicates psychological distress, and should always be taken seriously
  • A common motivation is emotional regulation, and self-injurious behaviours are perpetuated by positive or negative reinforcement
  • It is important to seek professional help for self-injury, such as counselling
  • An individual's acceptance of their self-injury as unhealthy along with the development of alternate coping mechanisms are helpful for recovery


How to get help

Helplines
Lifeline 24-Hour Counselling - 13 11 14
Kids Helpline - 1800 55 1800
Beyond Blue 24-hour Counselling - 1300 224 636

If it is an emergency, call 000 immediately

Test your knowledge[edit | edit source]

1 Self-injury ...?

Includes behaviours such as cutting and burning one's own skin
Is a coping mechanism
Is a deliberate behaviour
All of the above

2 True or False: Getting attention is the main motivator behind self-injury

TRUE
FALSE

3 How is self-injury different from a suicide attempt?

Self-injury and suicide attempts never co-occur
Self-injury is not intended to cause death
They are not different

4 The prevalence of self-injury is difficult to predict, partially due to it's secretive nature

TRUE
FALSE


See also[edit | edit source]

References[edit | edit source]

American Psychiatric Association. (2013). Conditions for further study. In Diagnostic and Statistical Manual of Mental Disorders (5th ed.).

Askew, M., & Byrne, M. W. (2009). Biopsychosocial approach to treating self-injurious behaviors: an adolescent case study. Journal of Child & Adolescent Psychiatric Nursing, 22(3), 115–119.

Bebko, G. M., Franconeri, S. L., Ochsner, K. N., & Chiao, J. Y. (2014). Attentional deployment is not necessary for successful emotion regulation via cognitive reappraisal or expressive suppression. Emotion, 14(3), 504-512.

Bresin, K., & Gordon, K.H. (2013). Endogenous opioids and nonsuicidal self-injury: A mechanism of affect regulation. Neuroscience and Biobehavioral Reviews, 37, 374-383.

Brockie, J. (Presenter). (2013, November 26). Scars. In J. Noyce (Senior Producer), Insight [Television broadcast]. Sydney, Australia: SBS. Retrieved from http://www.sbs.com.au/news/insight/tvepisode/scars

Chapman, A. L., Gratz, K. L., & Brown, M. Z. (2006). Solving the puzzle of deliberate self-harm: The experiential avoidance model. Behaviour Research and Therapy, 44 (3), 371-394.

Cook, A. et al. (2005). Complex trauma in Children and Adolescents. Psychiatric Annals, 35(5), 390-398.

Davenport, M. D., Lutz, C. K., Tiefenbacher, S., Novak, M. A., & Meyer, J.S. (2008) A rhesus monkey model of self-injury: effects of relocation stress on behavior and neuroendocrine function. Biological Psychiatry, 63, 990–996.

Gratz, K. L. (2006). Risk factors for deliberate self-harm among female college students: the role and interactions of childhood maltreatment, emotional inexpressivity, and affect intensity/reactivity. American Journal of Orthopsychiatry, 76, 238-250.

Headspace. (2013). National Youth Mental Health Foundation [Video file] Retrieved from http://www.headspace.org.au/about-headspace/news-videos/news/understanding-self-harm-video

Kakhnovets, R., Young, H. L., Purnell, A. L., Huebner, E., & Bishop, C. (2010). Self-reported experience of self-injurious behavior in college students. Journal of Mental Health Counseling, 32(4), 309-323.

Klonsky, E. D., & Lewis, S. P. (2014). Assessment of Non-Suicidal Self-Injury. In Nock, M. K. (Ed.), The Oxford Handbook of Suicide and Self-Injury (pp. 337-355). Oxford University Press, New York.

Laye-Gindhu, A. & Schonert-Reichl, A. S. (2005). Nonsuicidal self-harm among community adolescents: Understanding the “whats” and “whys” of self-harm. ‘’Journal of Youth and Adolescence, 34’’(5), 447-457

Martin, G., Swannell, S. V., Hazell, P. L., Harrison, J. E., & Taylor, A. W. (2010). Self-injury in Australia: a community survey. Medical Journal of Australia, 193(9), 506–510.

Menninger, K. Man Against Himself. New York: Harcourt, Brace & World.

Muehlenkamp, J. J., & Gutierrez, P. M. (2004). An Investigation of Differences Between Self-Injurious Behavior and Suicide Attempts in a Sample of :Adolescents. Suicide and Life-Threatening Behavior, 34(1), 12–23.

Nock, M. K., Prinstein, M. J., & Sterba, S. K. (2009). Revealing the Form and Function of Self-Injurious Thoughts and Behavior: A Real-Time Ecological Assessment Study Among Adolescents and Young Adults. Journal of Abnormal Psychology, 118(4), 816-827.

Paivio, S., & McCulloch, C. R. (2004). Alexithymia as a mediator between childhood trauma and self-injurious behaviors, Child Abuse and Neglect, 28, 339-354.

Polk, E., & Liss, M. (2007). Psychological characteristics of self-injurious behavior. Personality and Individual Differences, 43, 567-577.

Polk, E., & Liss, M. (2009). Exploring the motivations behind self-injury. Counselling Psychology Quarterly, 22(2), 233–241.

Posner, K., Brodsky, B., Yershova, K., Buchanan, J., & Mann, J. (2014). The Classification of Suicidal Behavior. In M. K. Nock (Ed.), The Oxford :Handbook of Suicide and Self-Injury (pp. 7–22). New York: Oxford University Press.

Purington, A., & Whitlock, J. (2010). Non-suicidal self-injury in the media. Prevention Researcher, 17(1), 11–13.

Stone, J. A., & Sias, S. M. (2003). Self-injurious behavior: A bimodal treatment approach to working with adolescent females. Journal of Mental Health Counseling, 25(2), 112-125.

Van der Kolk, B.A., Perry, J.C., & Herman, J.L. (1991). Childhood origins of self-destructive behavior. American Journal of Psychiatry, 148, 1665–1671.

Victor, S. E., Glenn, C. R., & Klonsky, E. D. (2012). Is non-suicidal self-injury an "addiction"? A comparison of craving in substance use and non-suicidal self-injury. Psychiatric Research, 197, 73-77.

Walsh, B. W. (2006). Treating self-injury: A practical guide. New York: Guilford Press.

Wichmann, S. S. (2011). Self-determination theory: The importance of autonomy to well-being across cultures. Journal of Humanistic Counseling, 50, 16-28.

Zlotnick, C., Mattia, J.I., & Zimmerman, M. (2001). The relationship between posttraumatic stress disorder, childhood trauma and alexithymia in an outpatient sample. Journal of Traumatic-Stress, 14(1): 177-188.


External links[edit | edit source]