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: Information on these effects could be obtained from angiograms of patients with cocaine - associated subarachnoid hemorrhage ( SAH ) who underwent angiography shortly after cocaine use .
### Output Text:
Information on these effects could be obtained from angiograms of patients with <span class="chemical">cocaine</span> - associated subarachnoid hemorrhage ( SAH ) who underwent angiography shortly after <span class="chemical">cocaine</span> use . 