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: Sixty patients ( age - range one month to 14 years ) with other types of epilepsy than infantile spasms were treated with clonazepam .
### Output Text:
Sixty patients ( age - range one month to 14 years ) with other types of epilepsy than infantile spasms were treated with <span class="chemical">clonazepam</span> . 