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: Etoricoxib and diclofenac treatment resulted in similar efficacy ( PGADS mean changes from baseline - 0 . 62 vs - 0 . 58 , respectively ) .
### Output Text:
<span class="chemical">Etoricoxib</span> and <span class="chemical">diclofenac</span> treatment resulted in similar efficacy ( PGADS mean changes from baseline - 0 . 62 vs - 0 . 58 , respectively ) . 