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 : There were more incidents of bradycardia in subjects treated with clonidine compared with those not treated with clonidine ( 17 . 5 % versus 3 . 4 % ; p = . 02 ) , but no other significant group differences regarding electrocardiogram and other cardiovascular outcomes .
### Output Text:
RESULTS : There were more incidents of bradycardia in subjects treated with <span class="chemical">clonidine</span> compared with those not treated with <span class="chemical">clonidine</span> ( 17 . 5 % versus 3 . 4 % ; p = . 02 ) , but no other significant group differences regarding electrocardiogram and other cardiovascular outcomes . 