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: The results evinced no enhancement of the hepatocarcinogenicity of the choline - devoid diet by phenobarbital .
### Output Text:
The results evinced no enhancement of the hepatocarcinogenicity of the <span class="chemical">choline</span> - devoid diet by <span class="chemical">phenobarbital</span> . 