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: STUDY HYPOTHESIS : Administration of the benzodiazepine antagonist flumazenil may unmask seizures in mixed cocaine - benzodiazepine intoxication .
### Output Text:
STUDY HYPOTHESIS : Administration of the <span class="chemical">benzodiazepine</span> antagonist <span class="chemical">flumazenil</span> may unmask seizures in mixed <span class="chemical">cocaine</span> - <span class="chemical">benzodiazepine</span> intoxication . 