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: METHODS : In type 2 diabetic patients , cases who developed CAD were compared retrospectively with controls that did not .
### Output Text:
METHODS : In type 2 diabetic patients , cases who developed CAD were compared retrospectively with controls that did not . 