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: End - systolic left ventricular posterior wall dimension at baseline for the doxorubicin - treated group was 11 + / - 1 . 9 mm versus 13 . 1 + / - 1 . 5 mm for control subjects ( p less than 0 . 01 ) .
### Output Text:
End - systolic left ventricular posterior wall dimension at baseline for the <span class="chemical">doxorubicin</span> - treated group was 11 + / - 1 . 9 mm versus 13 . 1 + / - 1 . 5 mm for control subjects ( p less than 0 . 01 ) . 