Exploring variation in human papillomavirus vaccination uptake in Switzerland: a multilevel spatial analysis of a national vaccination coverage survey - Riesen, M; Konstantinoudis, G; Lang, P; Low, N; Hatz, C; Maeusezahl, M; Spaar, A; Buhlmann, M; Spycher, BD; Althaus, CL (BMJ Open, 2018)