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 were 14 of 151 ( 9 . 3 % ) in the DFMO plus sulindac group and 4 of 139 ( 2 . 9 % ) in the placebo group who experienced at least 15 dB hearing reduction from baseline in 2 or more consecutive frequencies across the entire range tested ( P = 0 . 02 ) .
### Output Text:
There were 14 of 151 ( 9 . 3 % ) in the <span class="chemical">DFMO</span> plus <span class="chemical">sulindac</span> group and 4 of 139 ( 2 . 9 % ) in the placebo group who experienced at least 15 dB hearing reduction from baseline in 2 or more consecutive frequencies across the entire range tested ( P = 0 . 02 ) . 