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: CONCLUSION : Our results suggest the absolute risk of VTE among Danish women on COCs is similar to that among women taking CPA / EE .
### Output Text:
CONCLUSION : Our results suggest the absolute risk of VTE among Danish women on <span class="chemical">COCs</span> is similar to that among women taking <span class="chemical">CPA</span> / <span class="chemical">EE</span> . 