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: Postoperative delirium was assessed as defined by Diagnostic and Statistical Manual of Mental Disorders ( Third Edition Revised ) criteria using the Confusion Assessment Method beginning at any time from the second day after surgery .
### Output Text:
Postoperative delirium was assessed as defined by Diagnostic and Statistical Manual of Mental Disorders ( Third Edition Revised ) criteria using the Confusion Assessment Method beginning at any time from the second day after surgery . 