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: Our findings do suggest that CS - mediated protection is dependent on the action of the intact anionic CS molecule ( non - hydrolyzable CSE was as protective as CS ) , whose mechanism has yet to be defined .
### Output Text:
Our findings do suggest that <span class="chemical">CS</span> - mediated protection is dependent on the action of the intact anionic <span class="chemical">CS</span> molecule ( non - hydrolyzable <span class="chemical">CSE</span> was as protective as <span class="chemical">CS</span> ) , whose mechanism has yet to be defined . 