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: The patients with MD had a lower heart rate response to the test than all the other groups ( 2 - way analysis of variance , group by time interaction with Greenhouse - Geisser correction : F ( 3 , 762 ) = 2 . 85 , P = . 026 ) .
### Output Text:
The patients with MD had a lower heart rate response to the test than all the other groups ( 2 - way analysis of variance , group by time interaction with Greenhouse - Geisser correction : F ( 3 , 762 ) = 2 . 85 , P = . 026 ) . 