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: So far , 14 patients are evaluable for response ; of these , eight ( 57 % ) showed objective ( complete or partial ) response and disease stabilized in six patients .
### Output Text:
So far , 14 patients are evaluable for response ; of these , eight ( 57 % ) showed objective ( complete or partial ) response and disease stabilized in six patients . 