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: There was a significant difference in insulin sensitivity index among groups ( F ( 33 ) = 10 . 66 ; P < . 001 ) ( clozapine < olanzapine < risperidone ) , with subjects who received clozapine and olanzapine exhibiting significant insulin resistance compared with subjects who were treated with risperidone ( clozapine vs risperidone , t ( 33 ) = - 4 . 29 ; P < . 001 ; olanzapine vs risperidone , t ( 33 ) = - 3 . 62 ; P = . 001 [ P < . 001 ] ) .
### Output Text:
There was a significant difference in insulin sensitivity index among groups ( F ( 33 ) = 10 . 66 ; P < . 001 ) ( <span class="chemical">clozapine</span> < <span class="chemical">olanzapine</span> < <span class="chemical">risperidone</span> ) , with subjects who received <span class="chemical">clozapine</span> and <span class="chemical">olanzapine</span> exhibiting significant insulin resistance compared with subjects who were treated with <span class="chemical">risperidone</span> ( <span class="chemical">clozapine</span> vs <span class="chemical">risperidone</span> , t ( 33 ) = - 4 . 29 ; P < . 001 ; <span class="chemical">olanzapine</span> vs <span class="chemical">risperidone</span> , t ( 33 ) = - 3 . 62 ; P = . 001 [ P < . 001 ] ) . 