Assessment of health-related quality of life with the German SF-8. A comparison of telephone and postal survey modes

Erhart M, Wetzel R, Krügel A, Ravens-Sieberer U.
Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz. 2005 Dec;48(12):1322-9

https://www.ncbi.nlm.nih.gov/pubmed/16261299