Development and characterization of ceramic inserts Used in metallic resonators of EPR spectrometers to increase their sensitivity - S. V. Lemishko; I. P. Vorona; I. S. Holovina; V. O. Yukhymchuk; S. M. Okulov; V. V. Nosenko; S. O. Solopan; A. H. Bilous (Ukrainian Journal of Physics, 2021)