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 : Response rates did not significantly differ between olanzapine ( 43 . 7 % , 95 % CI = 28 . 8 % - 58 . 6 % ) and risperidone ( 54 . 3 % , 95 % CI = 39 . 9 % - 68 . 7 % ) .
### Output Text:
RESULTS : Response rates did not significantly differ between <span class="chemical">olanzapine</span> ( 43 . 7 % , 95 % CI = 28 . 8 % - 58 . 6 % ) and <span class="chemical">risperidone</span> ( 54 . 3 % , 95 % CI = 39 . 9 % - 68 . 7 % ) . 