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: After dipyridamole , ischemic ST - segment depression ( 0 . 05 mV or more ) was observed in 84 % of the non - MI group , 29 % of the ANT - MI group , 63 % of the INF - MI group and 61 % of the total population .
### Output Text:
After <span class="chemical">dipyridamole</span> , ischemic ST - segment depression ( 0 . 05 mV or more ) was observed in 84 % of the non - MI group , 29 % of the ANT - MI group , 63 % of the INF - MI group and 61 % of the total population . 