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: A 47 - year - old woman with right hydroureteronephrosis due to ureterovesical junction obstruction had gross hematuria after being treated for five years wtih cyclophosphamide for cerebral vasculitis .
### Output Text:
A 47 - year - old woman with right hydroureteronephrosis due to ureterovesical junction obstruction had gross hematuria after being treated for five years wtih <span class="chemical">cyclophosphamide</span> for cerebral vasculitis . 