response = requests.get(
    'http://www.ncbi.nlm.nih.gov/pubmed/?term=The%20cost-effectiveness%20of%20mirtazapine%20versus%20paroxetine%20in%20treating%20people%20with%20depression%20in%20primary%20care'
    )
namespaces = {'xi': 'http://www.w3.org/2001/XInclude', 'test':
    'http://www.w3.org/1999/xhtml'}
Using lxml to parse namepaced HTML?