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### Input Text: We also analyzed published and unpublished follow - up data to determine the risk of ICH in antithrombotic users with MB .
### Output Text:
We also analyzed published and unpublished follow - up data to determine the risk of ICH in antithrombotic users with MB . 