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 : This appears to be the first reported case documenting a possible association between CC and myocardial infarction .
### Output Text:
CONCLUSION : This appears to be the first reported case documenting a possible association between <span class="chemical">CC</span> and myocardial infarction . 