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 median cumulative doses of cyclophosphamide among cases ( n = 11 ) and controls ( n = 25 ) were 113 g and 25 g , respectively .
### Output Text:
RESULTS : The median cumulative doses of <span class="chemical">cyclophosphamide</span> among cases ( n = 11 ) and controls ( n = 25 ) were 113 g and 25 g , respectively . 