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: In phase A , extrapyramidal signs tended to be greater with the standard dose than in the other two conditions , primarily because of a subgroup ( 20 % ) who developed moderate to severe signs .
### Output Text:
In phase A , extrapyramidal signs tended to be greater with the standard dose than in the other two conditions , primarily because of a subgroup ( 20 % ) who developed moderate to severe signs . 