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 palpable venous cord was present in 23 % ( 14 of 62 ) of patients in the diazepam group , compared with 2 % ( 1 of 60 patients ) in the midazolam group ( p < 0 . 002 ) .
### Output Text:
A palpable venous cord was present in 23 % ( 14 of 62 ) of patients in the <span class="chemical">diazepam</span> group , compared with 2 % ( 1 of 60 patients ) in the <span class="chemical">midazolam</span> group ( p < 0 . 002 ) . 