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: Administration of 20 mg / kg / day CSA for 4 weeks caused renal functional and structural changes similar to those reported in man .
### Output Text:
Administration of 20 mg / kg / day <span class="chemical">CSA</span> for 4 weeks caused renal functional and structural changes similar to those reported in man . 