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: Our results support the view that MESNA , given orally in conjunction with combined cytostatic regimens which include IF , simplifies the treatment and provides optimum protection for the urinary epithelium .
### Output Text:
Our results support the view that <span class="chemical">MESNA</span> , given orally in conjunction with combined cytostatic regimens which include <span class="chemical">IF</span> , simplifies the treatment and provides optimum protection for the urinary epithelium . 