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: This study aimed to identify the molecular pathways and putative biomarkers of CsA - to - SRL conversion in a rat model .
### Output Text:
This study aimed to identify the molecular pathways and putative biomarkers of <span class="chemical">CsA</span> - to - <span class="chemical">SRL</span> conversion in a rat model . 