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: Among those responding to treatment , more subjects in the olanzapine group ( 40 . 9 % , 95 % CI = 16 . 8 % - 65 . 0 % ) than in the risperidone group ( 18 . 9 % , 95 % CI = 0 % - 39 . 2 % ) had subsequent ratings not meeting response criteria .
### Output Text:
Among those responding to treatment , more subjects in the <span class="chemical">olanzapine</span> group ( 40 . 9 % , 95 % CI = 16 . 8 % - 65 . 0 % ) than in the <span class="chemical">risperidone</span> group ( 18 . 9 % , 95 % CI = 0 % - 39 . 2 % ) had subsequent ratings not meeting response criteria . 