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: BACKGROUND : Cyproterone acetate combined with ethinyl estradiol ( CPA / EE ) is licensed in the UK for the treatment of women with acne and hirsutism and is also a treatment option for polycystic ovary syndrome ( PCOS ) .
### Output Text:
BACKGROUND : <span class="chemical">Cyproterone acetate</span> combined with <span class="chemical">ethinyl estradiol</span> ( <span class="chemical">CPA</span> / <span class="chemical">EE</span> ) is licensed in the UK for the treatment of women with acne and hirsutism and is also a treatment option for polycystic ovary syndrome ( PCOS ) . 