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: In order to examine this association , a case - control study with incident cases of ESRD was carried out .
### Output Text:
In order to examine this association , a case - control study with incident cases of ESRD was carried out . 