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: A randomized , placebo - controlled dose - comparison trial of haloperidol for psychosis and disruptive behaviors in Alzheimer ' s disease .
### Output Text:
A randomized , placebo - controlled dose - comparison trial of <span class="chemical">haloperidol</span> for psychosis and disruptive behaviors in Alzheimer ' s disease . 