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: No difference in the primary composite outcome in both the unmatched ( 30 % vs 30 % , p = 0 . 94 ) or matched cohorts ( 28 % vs 34 % , p = 0 . 35 ) could be found .
### Output Text:
No difference in the primary composite outcome in both the unmatched ( 30 % vs 30 % , p = 0 . 94 ) or matched cohorts ( 28 % vs 34 % , p = 0 . 35 ) could be found . 