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: Certain clues , including the onset of action , seem to be indicative of the superiority of bromperidol .
### Output Text:
Certain clues , including the onset of action , seem to be indicative of the superiority of <span class="chemical">bromperidol</span> . 