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: In addition to tiaprofenic acid , indomethacin has been reported to be associated with this condition .
### Output Text:
In addition to <span class="chemical">tiaprofenic acid</span> , <span class="chemical">indomethacin</span> has been reported to be associated with this condition . 