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: Groups of 5 - week old male Fischer - 344 rats were fed for 7 - 25 months semipurified choline - devoid or choline - supplemented diets , containing or not 0 . 06 % phenobarbital .
### Output Text:
Groups of 5 - week old male Fischer - 344 rats were fed for 7 - 25 months semipurified <span class="chemical">choline</span> - devoid or <span class="chemical">choline</span> - supplemented diets , containing or not 0 . 06 % <span class="chemical">phenobarbital</span> . 