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: The coronary vasodilating properties of nisoldipine have led to the investigation of this agent for use in angina .
### Output Text:
The coronary vasodilating properties of <span class="chemical">nisoldipine</span> have led to the investigation of this agent for use in angina . 