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: A phase III clinical trial assessed the recurrence of adenomatous polyps after treatment for 36 months with difluoromethylornithine ( DFMO ) plus sulindac or matched placebos .
### Output Text:
A phase III clinical trial assessed the recurrence of adenomatous polyps after treatment for 36 months with <span class="chemical">difluoromethylornithine</span> ( <span class="chemical">DFMO</span> ) plus <span class="chemical">sulindac</span> or matched placebos . 