1. Department of Behavioural Sciences and Psychiatry, College of Medicine, Sultan Qaboos University, PO Box 35, Al-Khoudh 123, Muscat, Sultanate of Oman. Tel/Fax: (968) 545203
2. Department of Mathematics and Statistics, Sultan Qaboos University, PO Box 36, Al-Khoudh 123, Muscat, Sultanate of Oman
3. Department of Physical Medicine and Rehabiliatation, Spaulding Rehabilitation Hospital, Harvard Medical School, 125 Nashua Street, Boston, MA 02114-1198, USA
4. Department of Behavioural Sciences and Psychiatry, College of Medicine, Sultan Qaboos University, PO Box 35, Al-Khoudh 123, Muscat, Sultanate of Oman
5. Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, 125 Nashua Street, Boston, MA 02114-1198, USA