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: DESIGN : The Expanded Clinical Evaluation of Lovastatin ( EXCEL ) Study , a multicenter , double - blind , diet - and placebo - controlled trial , in which participants were randomly assigned to receive placebo or lovastatin at doses of 20 or 40 mg once daily , or 20 or 40 mg twice daily for 48 weeks .
### Output Text:
DESIGN : The Expanded Clinical Evaluation of <span class="chemical">Lovastatin</span> ( EXCEL ) Study , a multicenter , double - blind , diet - and placebo - controlled trial , in which participants were randomly assigned to receive placebo or <span class="chemical">lovastatin</span> at doses of 20 or 40 mg once daily , or 20 or 40 mg twice daily for 48 weeks . 