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: BACKGROUND : We report on the manifestation of a levetiracetam ( LEV ) - induced encephalopathy .
### Output Text:
BACKGROUND : We report on the manifestation of a <span class="chemical">levetiracetam</span> ( <span class="chemical">LEV</span> ) - induced encephalopathy . 