The Diagnostic and Statistical Manual, vol V - the "bible" for psychologists and psychiatrists in figuring out what's what with their patients. If you find yourself dealing with a mental health professional, ask them if they agree with DSM-IV or DSM-V - if the latter, get away. DSM-V is the result of a group of morons who got commissioned by the American Psychiatric Assn, and they came up with stupidity like Aspergers and Autism are similar.