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: OBJECTIVE : To assess and characterise the risk of bladder cancer , and its relation to cyclophosphamide , in patients with Wegener ' s granulomatosis .
### Output Text:
OBJECTIVE : To assess and characterise the risk of bladder cancer , and its relation to <span class="chemical">cyclophosphamide</span> , in patients with Wegener ' s granulomatosis . 