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: CONCLUSION : This rat study demonstrated a synergistic nephrotoxic effect of CsA plus SRL , whereas FK506 plus SRL was better tolerated .
### Output Text:
CONCLUSION : This rat study demonstrated a synergistic nephrotoxic effect of <span class="chemical">CsA</span> plus <span class="chemical">SRL</span> , whereas <span class="chemical">FK506</span> plus <span class="chemical">SRL</span> was better tolerated . 