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: A patient with sinus bradycardia and atrioventricular block , induced by carbamazepine , prompted an extensive literature review of all previously reported cases .
### Output Text:
A patient with sinus bradycardia and atrioventricular block , induced by <span class="chemical">carbamazepine</span> , prompted an extensive literature review of all previously reported cases . 