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: Until now , the test has been focused only on the organic lesion in the coronary artery , and positive DSE has indicated the presence of significant fixed coronary artery stenosis .
### Output Text:
Until now , the test has been focused only on the organic lesion in the coronary artery , and positive DSE has indicated the presence of significant fixed coronary artery stenosis . 