1. American Psychiatric Association. Diagnostic and statistical manual of mental health disorders: DSM-IV-TR. 4th ed, text revision. Arlington, VA: American Psychiatric Association, 2000. (http://www.psych.org/research/dor/dsm/index.cfm).
2. World Health Organization. International classification of diseases. Tenth Revision, 2005 update. Geneva, Switzerland: World Health Organization, 2005. (http://www.who.int/classifications/icd/en/).
3. World Health Organization. The world health report 2001. Mental health: new understanding, new hope. Geneva, Switzerland: World Health Organization, 2001.
4. Murray CJL, Lopez AD, Mathers CD, et al. The global burden of disease 2000 project: aims, methods and data sources. Geneva, Switzerland: World Health Organization, 2002. (Paper 36). (http://www3.who.int/whosis/menu.cfm?path=whosis,burden,burden_gbd2000&language=english).
5. Henderson M, Glozier N, Holland Elliott K. Long term sickness absence. BMJ2005;330:802–3.