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: RESULTS : The results indicate that ciprofloxacin - and norfloxacin - treated rats showed anxious behaviour in comparison to control rats in all the parameters studied .
### Output Text:
RESULTS : The results indicate that <span class="chemical">ciprofloxacin</span> - and <span class="chemical">norfloxacin</span> - treated rats showed anxious behaviour in comparison to control rats in all the parameters studied . 