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: Rats treated with L - DOPA were allocated to two groups based on the presence or absence of LID .
### Output Text:
Rats treated with <span class="chemical">L - DOPA</span> were allocated to two groups based on the presence or absence of LID . 