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: METHOD : We searched the Eli Lilly and Company ' s computerized adverse event database for all reported cases of hyponatremia and / or SIADH as of 1 November 1999 that had been reported during the use of vincristine .
### Output Text:
METHOD : We searched the Eli Lilly and Company ' s computerized adverse event database for all reported cases of hyponatremia and / or SIADH as of 1 November 1999 that had been reported during the use of <span class="chemical">vincristine</span> . 