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: Moderate to high dose corticosteroid use is recognized as a major risk factor for SRC .
### Output Text:
Moderate to high dose <span class="chemical">corticosteroid</span> use is recognized as a major risk factor for SRC . 