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: CONCLUSIONS : The combination of paclitaxel , cisplatin , and gemcitabine is well tolerated and shows high activity in metastatic NSCLC .
### Output Text:
CONCLUSIONS : The combination of <span class="chemical">paclitaxel</span> , <span class="chemical">cisplatin</span> , and <span class="chemical">gemcitabine</span> is well tolerated and shows high activity in metastatic NSCLC . 