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: FINDINGS : 85 women met the inclusion criteria for VTE , two of whom were users of progestagen - only OCs .
### Output Text:
FINDINGS : 85 women met the inclusion criteria for VTE , two of whom were users of <span class="chemical">progestagen</span> - only <span class="chemical">OCs</span> . 