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: Dose reduction or concomitant steroid therapy may have a role in selected patients .
### Output Text:
Dose reduction or concomitant <span class="chemical">steroid</span> therapy may have a role in selected patients . 