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: After three days , a cumulative dosage of 200 mg of CE in refracted doses were given .
### Output Text:
After three days , a cumulative dosage of 200 mg of <span class="chemical">CE</span> in refracted doses were given . 