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: Gemfibrozil - lovastatin therapy for primary hyperlipoproteinemias .
### Output Text:
<span class="chemical">Gemfibrozil</span> - <span class="chemical">lovastatin</span> therapy for primary hyperlipoproteinemias . 