High-resolution spectroscopy, crystal-field calculations, and quadrupole helix chirality of DyFe3(BO3)4M.N. Popova, B.Z. Malkin, T.N. Stanislavchuk, E.P. Chukalina, K.N. Boldyrev and I.A. GudimEPJ Web Conf., 132 (2017) 03041DOI: https://doi.org/10.1051/epjconf/201713203041