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: Two phase II trials of 24 - hour paclitaxel infusions in chemotherapy - naive patients with stage IIIB or IV non - small cell lung cancer ( NSCLC ) reported response rates of 21 % and 24 % .
### Output Text:
Two phase II trials of 24 - hour <span class="chemical">paclitaxel</span> infusions in chemotherapy - naive patients with stage IIIB or IV non - small cell lung cancer ( NSCLC ) reported response rates of 21 % and 24 % . 