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: This effect undergoes rapid tolerance , showing a significant decrease after 2 days of sub - chronic L - NOARG treatment .
### Output Text:
This effect undergoes rapid tolerance , showing a significant decrease after 2 days of sub - chronic <span class="chemical">L - NOARG</span> treatment . 