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: Treatment of tacrolimus - related adverse effects by conversion to cyclosporine in liver transplant recipients .
### Output Text:
Treatment of <span class="chemical">tacrolimus</span> - related adverse effects by conversion to <span class="chemical">cyclosporine</span> in liver transplant recipients . 