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: CONCLUSION : This study confirms our previous finding that selegiline in combination with L - dopa is associated with selective orthostatic hypotension .
### Output Text:
CONCLUSION : This study confirms our previous finding that <span class="chemical">selegiline</span> in combination with <span class="chemical">L - dopa</span> is associated with selective orthostatic hypotension . 