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: Additional studies of these murine strains may be useful for investigating genetic influences on cocaine - induced seizures .
### Output Text:
Additional studies of these murine strains may be useful for investigating genetic influences on <span class="chemical">cocaine</span> - induced seizures . 