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: Hepatic mRNA levels of CYP7A were significantly reduced by EE in bile - diverted rats only ; CYP27 mRNA levels were not affected by EE .
### Output Text:
Hepatic mRNA levels of CYP7A were significantly reduced by <span class="chemical">EE</span> in bile - diverted rats only ; CYP27 mRNA levels were not affected by <span class="chemical">EE</span> . 