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: 51 patients with medically refractory Parkinson ' s disease underwent stereotactic posteromedial pallidotomy between August 1993 and February 1997 for treatment of bradykinesia , rigidity , and L - DOPA - induced dyskinesias .
### Output Text:
51 patients with medically refractory Parkinson ' s disease underwent stereotactic posteromedial pallidotomy between August 1993 and February 1997 for treatment of bradykinesia , rigidity , and <span class="chemical">L - DOPA</span> - induced dyskinesias . 