In subvolume 27C1 magnetic and related properties of binary lanthanide oxides have been compiled. This subvolume covers data obtained since 1980 and can therefore be regarded as supplement to volume III/12c. While in the previous volume the majority of magnetic data was obtained either from magnetometric measurements or from neutron diffraction, for the present data the main emphasis is devoted to "related" properties without which, however, the understanding of classical magnetic properties is impossible. A second part 27C2 will deal with binary oxides of the actinide elements.