Zampelis, Vasilis, et al. “A Simple Visual Analog Scale for Pain Is As Responsive As the WOMAC, the SF-36, and the EQ-5D in Measuring Outcomes of Revision Hip Arthroplasty”. Acta Orthopaedica, vol. 85, no. 2, Apr. 2014, pp. 128-32, doi:10.3109/17453674.2014.887951.