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: Similarly , all adenosine receptor agonists decreased amphetamine - induced hyperactivity , but at the higher doses than those which were active in cocaine - induced hyperactivity .
### Output Text:
Similarly , all <span class="chemical">adenosine</span> receptor agonists decreased <span class="chemical">amphetamine</span> - induced hyperactivity , but at the higher doses than those which were active in <span class="chemical">cocaine</span> - induced hyperactivity . 