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: Two studies evaluated quetiapine monotherapy ( up to 800 mg / day ) ( n = 209 ) versus placebo ( n = 198 ) , with lithium or haloperidol monotherapy as respective active controls .
### Output Text:
Two studies evaluated <span class="chemical">quetiapine</span> monotherapy ( up to 800 mg / day ) ( n = 209 ) versus placebo ( n = 198 ) , with <span class="chemical">lithium</span> or <span class="chemical">haloperidol</span> monotherapy as respective active controls . 