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: With cocaine , the drug concentration in blood obtained from the coronary sinus was 3 . 0 + / - 0 . 4 ( mean + / - SD ) mg / L , similar in magnitude to the blood cocaine concentration reported in abusers dying of cocaine intoxication .
### Output Text:
With <span class="chemical">cocaine</span> , the drug concentration in blood obtained from the coronary sinus was 3 . 0 + / - 0 . 4 ( mean + / - SD ) mg / L , similar in magnitude to the blood <span class="chemical">cocaine</span> concentration reported in abusers dying of <span class="chemical">cocaine</span> intoxication . 