K. D. Litasov, A. F. Shatskiy, S. G. Ovchinnikov, Z. I. Popov, D. S. Ponomarev, E. Ohtani, “Phase transformations of Fe$_3$N-Fe$_4$N iron nitrides at pressures up to $30$ GPa studied by in situ X-ray diffractometry”, Pis'ma v Zh. Èksper. Teoret. Fiz., 98:12 (2013), 907–911; JETP Letters, 98:12 (2013), 805–808
