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: Risk of coronary artery disease associated with initial sulphonylurea treatment of patients with type 2 diabetes : a matched case - control study .
### Output Text:
Risk of coronary artery disease associated with initial <span class="chemical">sulphonylurea</span> treatment of patients with type 2 diabetes : a matched case - control study . 