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: Levodopa - induced dyskinesia of the limbs in thirteen cases of Parkinsonism , which was choreic , ballistic or dystonic in type , was alleviated almost completely by stereotaxic surgery using a microelectrode technique for the ventralis oralis anterior and posterior nuclei of the thalamus , but much less by the ventralis intermedius nucleus .
### Output Text:
<span class="chemical">Levodopa</span> - induced dyskinesia of the limbs in thirteen cases of Parkinsonism , which was choreic , ballistic or dystonic in type , was alleviated almost completely by stereotaxic surgery using a microelectrode technique for the ventralis oralis anterior and posterior nuclei of the thalamus , but much less by the ventralis intermedius nucleus . 