There are currently 4 sets of Asperger Syndrome Criteria:
Gillberg and Gillberg (1989)
Szatmari, Bremner and Nagy (1989)
ICD-10 (World Health Organization, 1993)
It is interesting to note that these criteria are all slightly different, with some more inclusive of individuals on the spectrum and some more exclusive (strict). The criteria are listed in appendices in Tony Attwood, Aspergerís Syndrome, A Guide for Parents and Professionals, Jessica Kingsley Publishers, 1998.