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: There are no published ASA studies using the multiple dosing paradigm of GDs 6 to 17 .
### Output Text:
There are no published <span class="chemical">ASA</span> studies using the multiple dosing paradigm of GDs 6 to 17 . 