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 recommended dose of 500 mg / m2 / d delivers a total dose of 7 g / m2 per cycle , which is comparable to that delivered in clinical practice for bolus or short - term infusion .
### Output Text:
The recommended dose of 500 mg / m2 / d delivers a total dose of 7 g / m2 per cycle , which is comparable to that delivered in clinical practice for bolus or short - term infusion . 