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: Dose - limiting toxicities in six of nine patients at 200 mg / m2 / d included hypercalcemia ( n = 3 ) , rash ( n = 2 ) , and anemia / thrombocytopenia / emesis / rash ( n = 1 ) .
### Output Text:
Dose - limiting toxicities in six of nine patients at 200 mg / m2 / d included hypercalcemia ( n = 3 ) , rash ( n = 2 ) , and anemia / thrombocytopenia / emesis / rash ( n = 1 ) . 