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: Preventive Services Task Force ( USPSTF ) strongly recommended that clinicians discuss aspirin with adults who are at increased risk for coronary heart disease .
### Output Text:
Preventive Services Task Force ( USPSTF ) strongly recommended that clinicians discuss <span class="chemical">aspirin</span> with adults who are at increased risk for coronary heart disease . 