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: A total of 115 patients with a DSM - IV diagnosis of bipolar disorder , manic or mixed , were randomized to olanzapine , 5 to 20 mg / d ( n = 55 ) , or placebo ( n = 60 ) .
### Output Text:
A total of 115 patients with a DSM - IV diagnosis of bipolar disorder , manic or mixed , were randomized to <span class="chemical">olanzapine</span> , 5 to 20 mg / d ( n = 55 ) , or placebo ( n = 60 ) . 