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: The effects of oral doses of diazepam ( single dose of 10 mg and a median dose of 30 mg / day for 2 weeks ) and propranolol ( single dose of 80 mg and a median dose of 240 mg / day for 2 weeks ) on psychological performance of patients with panic disorders and agoraphobia were investigated in a double - blind , randomized and crossover design .
### Output Text:
The effects of oral doses of <span class="chemical">diazepam</span> ( single dose of 10 mg and a median dose of 30 mg / day for 2 weeks ) and <span class="chemical">propranolol</span> ( single dose of 80 mg and a median dose of 240 mg / day for 2 weeks ) on psychological performance of patients with panic disorders and agoraphobia were investigated in a double - blind , randomized and crossover design . 