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: Of the benzodiazepines , clonazepam ( 0 . 1 - 0 . 3 mg / kg ) was found to be several fold more potent than diazepam ( 0 . 3 - 3 mg / kg ) in blocking the myoclonic jerks .
### Output Text:
Of the <span class="chemical">benzodiazepines</span> , <span class="chemical">clonazepam</span> ( 0 . 1 - 0 . 3 mg / kg ) was found to be several fold more potent than <span class="chemical">diazepam</span> ( 0 . 3 - 3 mg / kg ) in blocking the myoclonic jerks . 