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: Lithium was associated with a significantly higher incidence ( p < 0 . 05 ) of tremor ( 18 . 4 % ) than quetiapine ( 5 . 6 % ) ; cerebellar tremor , which is a known adverse effect of lithium , may have contributed to the elevated rate of tremor in patients receiving lithium therapy .
### Output Text:
<span class="chemical">Lithium</span> was associated with a significantly higher incidence ( p < 0 . 05 ) of tremor ( 18 . 4 % ) than <span class="chemical">quetiapine</span> ( 5 . 6 % ) ; cerebellar tremor , which is a known adverse effect of <span class="chemical">lithium</span> , may have contributed to the elevated rate of tremor in patients receiving <span class="chemical">lithium</span> therapy . 