In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: METHOD : Medically healthy 7 - to 17 - year - old males chronically treated , in a naturalistic setting , with risperidone were recruited for this cross - sectional study through child psychiatry outpatient clinics between November 2005 and June 2007 .
### Output Text:
METHOD : Medically healthy 7 - to 17 - year - old males chronically treated , in a naturalistic setting , with <span class="chemical">risperidone</span> were recruited for this cross - sectional study through child psychiatry outpatient clinics between November 2005 and June 2007 . 