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: Patients scoring > or = 20 MMSE sum points were interviewed ( n = 79 ) and questioned regarding symptoms and functional abilities during the week prior to admission .
### Output Text:
Patients scoring > or = 20 MMSE sum points were interviewed ( n = 79 ) and questioned regarding symptoms and functional abilities during the week prior to admission . 