L. E. Svistov, L. A. Prozorova, N. Büttgen, A. Ya. Shapiro, L. N. Dem’yanets, “$^{87}$Rb NMR study of the magnetic structure of the quasi-two-dimensional antiferromagnet RbFe(MoO$_4$)$_2$ on a triangular lattice”, Pis'ma v Zh. Èksper. Teoret. Fiz., 81:3 (2005), 133–138; JETP Letters, 81:3 (2005), 102–107
