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: RESULTS : The age - adjusted incidence rate ratio for CPA / EE versus conventional COCs was 2 . 20 [ 95 % confidence interval ( CI ) 1 . 35 - 3 . 58 ] .
### Output Text:
RESULTS : The age - adjusted incidence rate ratio for <span class="chemical">CPA</span> / <span class="chemical">EE</span> versus conventional COCs was 2 . 20 [ 95 % confidence interval ( CI ) 1 . 35 - 3 . 58 ] . 