Simplify the following text for a Grade 12 native English-speaking person.
Original: AS became a standard diagnosis in 1992 , when it was included in the tenth edition of the World Health Organization 's diagnostic manual , International Classification of Diseases ( ICD-10 ) ; in 1994 , it was added to the fourth edition of the American Psychiatric Association 's diagnostic reference , Diagnostic and Statistical Manual of Mental Disorders ( DSM-IV ) .
Simplified: In 1994 Asperger Syndrome was added to the Diagnostic and Statistical Manual of Mental Disorders ( DSM-IV ) .