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: These results fail to support the notion that levodopa - induced dyskinesias are caused by overstimulation of a separate group of dopamine receptors .
### Output Text:
These results fail to support the notion that <span class="chemical">levodopa</span> - induced dyskinesias are caused by overstimulation of a separate group of <span class="chemical">dopamine</span> receptors . 