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: Efficacy and safety of asenapine in a placebo - and haloperidol - controlled trial in patients with acute exacerbation of schizophrenia .
### Output Text:
Efficacy and safety of <span class="chemical">asenapine</span> in a placebo - and <span class="chemical">haloperidol</span> - controlled trial in patients with acute exacerbation of schizophrenia . 