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: Median overall survival time was 10 . 2 months [ 95 % confidence interval ( CI ) : 8 . 7 - 11 . 6 ] , and median progression - free survival time was 7 . 6 months ( 95 % CI : 4 . 4 - 10 . 9 ) .
### Output Text:
Median overall survival time was 10 . 2 months [ 95 % confidence interval ( CI ) : 8 . 7 - 11 . 6 ] , and median progression - free survival time was 7 . 6 months ( 95 % CI : 4 . 4 - 10 . 9 ) . 