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: Sales statistics of COCs and CPA / EE were provided through Danish Drug Statistics .
### Output Text:
Sales statistics of <span class="chemical">COCs</span> and <span class="chemical">CPA</span> / <span class="chemical">EE</span> were provided through Danish Drug Statistics . 