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: Finally , two mechanisms at least , direct vasodilation and flow dependency , are involved in the cromakalim - and pinacidil - induced increase in CxAD .
### Output Text:
Finally , two mechanisms at least , direct vasodilation and flow dependency , are involved in the <span class="chemical">cromakalim</span> - and <span class="chemical">pinacidil</span> - induced increase in CxAD . 