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: Although increased risk of thromboembolic disease has been reported during treatment with epsilon - aminocaproic acid , cerebral sinus thrombosis has not been previously described .
### Output Text:
Although increased risk of thromboembolic disease has been reported during treatment with <span class="chemical">epsilon - aminocaproic acid</span> , cerebral sinus thrombosis has not been previously described . 