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: CONCLUSION : In this preliminary study patients submitted to PTRA showed a lower susceptibility to renal damage induced by CM administration than PCI patients .
### Output Text:
CONCLUSION : In this preliminary study patients submitted to PTRA showed a lower susceptibility to renal damage induced by <span class="chemical">CM</span> administration than PCI patients . 