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: Gemcitabine plus vinorelbine in nonsmall cell lung carcinoma patients age 70 years or older or patients who cannot receive cisplatin .
### Output Text:
<span class="chemical">Gemcitabine</span> plus <span class="chemical">vinorelbine</span> in nonsmall cell lung carcinoma patients age 70 years or older or patients who cannot receive <span class="chemical">cisplatin</span> . 