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: The present study describes the delayed development of a severe bladder pathology in a susceptible strain of mice ( DBA / 2 ) but not in a resistant strain ( C57BL / 6 ) when both were treated with a single 300 mg / kg dose of cyclophosphamide ( CY ) .
### Output Text:
The present study describes the delayed development of a severe bladder pathology in a susceptible strain of mice ( DBA / 2 ) but not in a resistant strain ( C57BL / 6 ) when both were treated with a single 300 mg / kg dose of <span class="chemical">cyclophosphamide</span> ( <span class="chemical">CY</span> ) . 