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: RESULTS : In a pooled analysis of 1460 ICH and 3817 IS / TIA , MB were more frequent in ICH vs IS / TIA in all treatment groups , but the excess increased from 2 . 8 ( odds ratio ; range , 2 . 3 - 3 . 5 ) in nonantithrombotic users to 5 . 7 ( range , 3 . 4 - 9 . 7 ) in antiplatelet users and 8 . 0 ( range , 3 . 5 - 17 . 8 ) in warfarin users ( P difference = 0 . 01 ) .
### Output Text:
RESULTS : In a pooled analysis of 1460 ICH and 3817 IS / TIA , MB were more frequent in ICH vs IS / TIA in all treatment groups , but the excess increased from 2 . 8 ( odds ratio ; range , 2 . 3 - 3 . 5 ) in nonantithrombotic users to 5 . 7 ( range , 3 . 4 - 9 . 7 ) in antiplatelet users and 8 . 0 ( range , 3 . 5 - 17 . 8 ) in <span class="chemical">warfarin</span> users ( P difference = 0 . 01 ) . 