Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3D Galactic halo magnetic field. - Sobey, C; Bilous, A V; Grießmeier, J-M; Hessels, J W T; Karastergiou, A; Keane, E F; Kondratiev, V I; Kramer, M; Michilli, D; Noutsos, A; Pilia, M; Polzin, E J; et al. (Monthly Notices of the Royal Astronomical Society, 2019)