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: Animals with a tumor ( diameter , 15 . 8 + / - 3 . 3 mm ) were treated with iv injections of doxorubicin on 5 consecutive days , followed by 1 weekly injection for 7 weeks ( dose range , 0 . 015 - 4 . 0 mg / kg body wt ) .
### Output Text:
Animals with a tumor ( diameter , 15 . 8 + / - 3 . 3 mm ) were treated with iv injections of <span class="chemical">doxorubicin</span> on 5 consecutive days , followed by 1 weekly injection for 7 weeks ( dose range , 0 . 015 - 4 . 0 mg / kg body wt ) . 