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: A further deterioration was seen when CsA was combined with either FK506 or SRL , whereas the GFR remained unchanged in the group treated with FK506 plus SRL when compared with treatment with any of the single substances .
### Output Text:
A further deterioration was seen when <span class="chemical">CsA</span> was combined with either <span class="chemical">FK506</span> or <span class="chemical">SRL</span> , whereas the GFR remained unchanged in the group treated with <span class="chemical">FK506</span> plus <span class="chemical">SRL</span> when compared with treatment with any of the single substances . 