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: Here we compare the time course of levodopa - induced motor fluctuations and neuropsychiatric - like behaviors to determine the relationship between duration of treatment and onset of symptoms .
### Output Text:
Here we compare the time course of <span class="chemical">levodopa</span> - induced motor fluctuations and neuropsychiatric - like behaviors to determine the relationship between duration of treatment and onset of symptoms . 