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: METHODS : Seventy - five patients with non - Hodgkin lymphoma treated with epirubicin were studied .
### Output Text:
METHODS : Seventy - five patients with non - Hodgkin lymphoma treated with <span class="chemical">epirubicin</span> were studied . 