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: Pallidal stimulation improves bradykinesia and rigidity to a minor extent ; however , its strength seems to be in improving levodopa - induced dyskinesias .
### Output Text:
Pallidal stimulation improves bradykinesia and rigidity to a minor extent ; however , its strength seems to be in improving <span class="chemical">levodopa</span> - induced dyskinesias . 