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: Drug - induced parkinsonism was observed in subjects treated with risperidone ( 42 % ) and haloperidol ( 29 % ) and was observed at occupancy levels above 60 % .
### Output Text:
Drug - induced parkinsonism was observed in subjects treated with <span class="chemical">risperidone</span> ( 42 % ) and <span class="chemical">haloperidol</span> ( 29 % ) and was observed at occupancy levels above 60 % . 