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: Tiapride had no effect on levodopa - induced early morning of " off - period " segmental dystonia .
### Output Text:
<span class="chemical">Tiapride</span> had no effect on <span class="chemical">levodopa</span> - induced early morning of " off - period " segmental dystonia . 