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: OUTCOME : Following discontinuation of LEV , EEG and neuropsychological findings improved and seizure frequency decreased .
### Output Text:
OUTCOME : Following discontinuation of <span class="chemical">LEV</span> , EEG and neuropsychological findings improved and seizure frequency decreased . 