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: Combination therapy is associated with a clinically important adverse effect : ribavirin - induced hemolytic anemia ( RIHA ) .
### Output Text:
Combination therapy is associated with a clinically important adverse effect : <span class="chemical">ribavirin</span> - induced hemolytic anemia ( RIHA ) . 