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: Lovastatin and simvastatin are the 2 best - known members of the class of hypolipidaemic agents known as HMG CoA reductase inhibitors .
### Output Text:
<span class="chemical">Lovastatin</span> and <span class="chemical">simvastatin</span> are the 2 best - known members of the class of hypolipidaemic agents known as HMG CoA reductase inhibitors . 