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: In six dogs with doxorubicin - induced heart failure , VIP decreased from 31 + / - 7 to 11 + / - 4 pg / mg protein ( P less than 0 . 05 ) .
### Output Text:
In six dogs with <span class="chemical">doxorubicin</span> - induced heart failure , VIP decreased from 31 + / - 7 to 11 + / - 4 pg / mg protein ( P less than 0 . 05 ) . 