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: RESULTS : Among 593 patients with cerebral haemorrhage , 59 ( 10 % ) were assessed as related to warfarin treatment .
### Output Text:
RESULTS : Among 593 patients with cerebral haemorrhage , 59 ( 10 % ) were assessed as related to <span class="chemical">warfarin</span> treatment . 