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: Although most of the hepatomas were well - differentiated tumors and contained a considerable number of peroxisomes , the tumor cells did not respond to ethyl - alpha - p - chlorophenoxyisobutyrate with proliferation of peroxisomes .
### Output Text:
Although most of the hepatomas were well - differentiated tumors and contained a considerable number of peroxisomes , the tumor cells did not respond to <span class="chemical">ethyl - alpha - p - chlorophenoxyisobutyrate</span> with proliferation of peroxisomes . 