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: RESULTS : Fourteen patients ( 18 . 67 % ) developed cardiotoxicity after treatment .
### Output Text:
RESULTS : Fourteen patients ( 18 . 67 % ) developed cardiotoxicity after treatment . 