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: Eleven of the cocaine abusers and none of the controls had ECG evidence of significant myocardial injury defined as myocardial infarction , ischemia , and bundle branch block .
### Output Text:
Eleven of the <span class="chemical">cocaine</span> abusers and none of the controls had ECG evidence of significant myocardial injury defined as myocardial infarction , ischemia , and bundle branch block . 