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: OBJECTIVES : The United Kingdom Parkinson ' s Disease Research Group ( UKPDRG ) trial found an increased mortality in patients with Parkinson ' s disease ( PD ) randomized to receive 10 mg selegiline per day and L - dopa compared with those taking L - dopa alone .
### Output Text:
OBJECTIVES : The United Kingdom Parkinson ' s Disease Research Group ( UKPDRG ) trial found an increased mortality in patients with Parkinson ' s disease ( PD ) randomized to receive 10 mg <span class="chemical">selegiline</span> per day and <span class="chemical">L - dopa</span> compared with those taking <span class="chemical">L - dopa</span> alone . 