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: CONCLUSIONS : The combination of cisplatin and amifostine in this study resulted in an overall response rate of 16 % .
### Output Text:
CONCLUSIONS : The combination of <span class="chemical">cisplatin</span> and <span class="chemical">amifostine</span> in this study resulted in an overall response rate of 16 % . 