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: Fasting serum insulin concentrations differed among groups ( F ( 33 ) = 3 . 35 ; P = . 047 ) ( clozapine > olanzapine > risperidone ) with significant differences between clozapine and risperidone ( t ( 33 ) = 2 . 32 ; P = . 03 ) and olanzapine and risperidone ( t ( 33 ) = 2 . 15 ; P = . 04 ) .
### Output Text:
Fasting serum insulin concentrations differed among groups ( F ( 33 ) = 3 . 35 ; P = . 047 ) ( <span class="chemical">clozapine</span> > <span class="chemical">olanzapine</span> > <span class="chemical">risperidone</span> ) with significant differences between <span class="chemical">clozapine</span> and <span class="chemical">risperidone</span> ( t ( 33 ) = 2 . 32 ; P = . 03 ) and <span class="chemical">olanzapine</span> and <span class="chemical">risperidone</span> ( t ( 33 ) = 2 . 15 ; P = . 04 ) . 