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: Dipyridamole significantly increased coronary blood flow before and after 7 . 5 or 15 mm / kg i . v . pentoxifylline ( p less than 0 . 002 ) .
### Output Text:
<span class="chemical">Dipyridamole</span> significantly increased coronary blood flow before and after 7 . 5 or 15 mm / kg i . v . <span class="chemical">pentoxifylline</span> ( p less than 0 . 002 ) . 