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: Thirty - four patients with juvenile rheumatoid arthritis , who were treated with flurbiprofen at a maximum dose of 4 mg / kg / day , had statistically significant decreases from baseline in 6 arthritis indices after 12 weeks of treatment .
### Output Text:
Thirty - four patients with juvenile rheumatoid arthritis , who were treated with <span class="chemical">flurbiprofen</span> at a maximum dose of 4 mg / kg / day , had statistically significant decreases from baseline in 6 arthritis indices after 12 weeks of treatment . 