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: Treatment for ticlopidine - induced aplastic anemia with colony - stimulating factors seemed to have little effect .
### Output Text:
Treatment for <span class="chemical">ticlopidine</span> - induced aplastic anemia with colony - stimulating factors seemed to have little effect . 