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: For low - dose nimodipine , the results were not conclusive .
### Output Text:
For low - dose <span class="chemical">nimodipine</span> , the results were not conclusive . 