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: Phenobarbitone - induced enlargement of the liver in the rat : its relationship to carbon tetrachloride - induced cirrhosis .
### Output Text:
<span class="chemical">Phenobarbitone</span> - induced enlargement of the liver in the rat : its relationship to <span class="chemical">carbon tetrachloride</span> - induced cirrhosis . 