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: Neither dose of pentoxifylline significantly decreased the dipyridamole - induced hyperemia , while peak coronary blood flow was significantly lower after theophylline ( p less than 0 . 01 ) .
### Output Text:
Neither dose of <span class="chemical">pentoxifylline</span> significantly decreased the <span class="chemical">dipyridamole</span> - induced hyperemia , while peak coronary blood flow was significantly lower after <span class="chemical">theophylline</span> ( p less than 0 . 01 ) . 