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: Phase II study of the amsacrine analogue CI - 921 ( NSC 343499 ) in non - small cell lung cancer .
### Output Text:
Phase II study of the <span class="chemical">amsacrine</span> analogue <span class="chemical">CI - 921</span> ( <span class="chemical">NSC 343499</span> ) in non - small cell lung cancer . 