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 incidence of preneoplastic nodules and of hepatocellular carcinomas was 10 % and 37 % , respectively , in rats fed the plain choline - devoid diet , and 17 % and 30 % , in rats fed the phenobarbital - containing choline - devoid diet .
### Output Text:
The incidence of preneoplastic nodules and of hepatocellular carcinomas was 10 % and 37 % , respectively , in rats fed the plain <span class="chemical">choline</span> - devoid diet , and 17 % and 30 % , in rats fed the <span class="chemical">phenobarbital</span> - containing <span class="chemical">choline</span> - devoid diet . 