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: RESULTS : Of 292 subjects , 47 . 9 % of the subjects had a past history of psychotic symptoms and 13 . 0 % of the patients were having current psychotic symptoms .
### Output Text:
RESULTS : Of 292 subjects , 47 . 9 % of the subjects had a past history of psychotic symptoms and 13 . 0 % of the patients were having current psychotic symptoms . 