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: The aim of this study was to assess the efficacy of Ro15 - 1788 and a placebo in reversing diazepam - induced effects after surgery under epidural block , and to evaluate the local tolerance and general safety of Ro15 - 1788 .
### Output Text:
The aim of this study was to assess the efficacy of <span class="chemical">Ro15 - 1788</span> and a placebo in reversing <span class="chemical">diazepam</span> - induced effects after surgery under epidural block , and to evaluate the local tolerance and general safety of <span class="chemical">Ro15 - 1788</span> . 