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: In a number of treatment protocols where SRL was combined with a calcineurin inhibitor indications of a synergistic nephrotoxic effect were described .
### Output Text:
In a number of treatment protocols where <span class="chemical">SRL</span> was combined with a calcineurin inhibitor indications of a synergistic nephrotoxic effect were described . 