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 phase I trial was designed to determine the maximal - tolerated dosage ( MTD ) , toxicities , and pharmacokinetics of cis - RA administered on an intermittent schedule in children with neuroblastoma following bone marrow transplantation ( BMT ) .
### Output Text:
This phase I trial was designed to determine the maximal - tolerated dosage ( MTD ) , toxicities , and pharmacokinetics of <span class="chemical">cis - RA</span> administered on an intermittent schedule in children with neuroblastoma following bone marrow transplantation ( BMT ) . 