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: Anticoagulant - induced femoral nerve palsy represents the most common form of warfarin - induced peripheral neuropathy ; it is characterized by severe pain in the inguinal region , varying degrees of motor and sensory impairment , and flexure contracture of the involved extremity .
### Output Text:
Anticoagulant - induced femoral nerve palsy represents the most common form of <span class="chemical">warfarin</span> - induced peripheral neuropathy ; it is characterized by severe pain in the inguinal region , varying degrees of motor and sensory impairment , and flexure contracture of the involved extremity . 