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: Four animal groups ( n = 6 ) were tested during 9 weeks : control , CsA , SRL , and conversion ( CsA for 3 weeks followed by SRL for 6 weeks ) .
### Output Text:
Four animal groups ( n = 6 ) were tested during 9 weeks : control , <span class="chemical">CsA</span> , <span class="chemical">SRL</span> , and conversion ( <span class="chemical">CsA</span> for 3 weeks followed by <span class="chemical">SRL</span> for 6 weeks ) . 