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 goal of the study was to deliver a dose rate and total cumulative dose of ifosfamide that would be comparable to standard bolus or short - term infusions administered with Mesna .
### Output Text:
The goal of the study was to deliver a dose rate and total cumulative dose of <span class="chemical">ifosfamide</span> that would be comparable to standard bolus or short - term infusions administered with <span class="chemical">Mesna</span> . 