Ferrite cores - Guidelines on dimensions and the limits of surface irregularities - Part 12: Ring-cores (IEC 63093-12:2019); German version EN IEC 63093-12:2019— 20 стр.
Terms and nomenclature for cores made of magnetically soft ferrites - Part 2: Reference of dimensions (IEC 60401-2:2009); German version EN 60401-2:2010— 10 стр.