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: Although many other factors such as sensitization may play a role , intensity of stimulant - induced psychotic symptoms and stereotypies appears to be at least in part dose - related .
### Output Text:
Although many other factors such as sensitization may play a role , intensity of stimulant - induced psychotic symptoms and stereotypies appears to be at least in part dose - related . 