PACS:07.60.Ly, 06.30.Bp, 85.60.−q (all) DOI:10.1070/PU1972v015n02ABEH004966 URL: https://ufn.ru/en/articles/1972/2/h/ Citation: Kartashev A I, Etsin I Sh "Methods of Measuring Small Phase Difference Changes in Interference Devices" Sov. Phys. Usp.15 232–250 (1972)