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: A series of agents acting primarily on neurotransmitters other than dopamine were then tested in combination with L - DOPA to see if the dyskinetic movements would be modified .
### Output Text:
A series of agents acting primarily on neurotransmitters other than <span class="chemical">dopamine</span> were then tested in combination with <span class="chemical">L - DOPA</span> to see if the dyskinetic movements would be modified . 