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: These findings indicate that dobutamine can provoke coronary spasm in some patients with coronary spastic angina .
### Output Text:
These findings indicate that <span class="chemical">dobutamine</span> can provoke coronary spasm in some patients with coronary spastic angina . 