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 significant correlation was found between baseline TAFI antigen concentrations and the duration of amenorrhea ( P < 0 . 05 ; r = 0 . 33 ) .
### Output Text:
A significant correlation was found between baseline TAFI antigen concentrations and the duration of amenorrhea ( P < 0 . 05 ; r = 0 . 33 ) . 