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: Groups 3 and 4 were studied at four and at six months to assess the effect of enalapril on progression of renal injury in adriamycin nephrosis .
### Output Text:
Groups 3 and 4 were studied at four and at six months to assess the effect of <span class="chemical">enalapril</span> on progression of renal injury in <span class="chemical">adriamycin</span> nephrosis . 