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: Although the overall reported rate of SIADH associated with vincristine is very low , physicians caring for Asian oncology patients should be aware of this potential serious but reversible adverse event .
### Output Text:
Although the overall reported rate of SIADH associated with <span class="chemical">vincristine</span> is very low , physicians caring for Asian oncology patients should be aware of this potential serious but reversible adverse event . 