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 : In the amphetamine - induced locomotion test , there were significant increases in all movements compared with the amphetamine - free group .
### Output Text:
RESULTS : In the <span class="chemical">amphetamine</span> - induced locomotion test , there were significant increases in all movements compared with the <span class="chemical">amphetamine</span> - free group . 