PACS:98.35.−a, 95.30.Lz (all) DOI:10.1070/PU1993v036n03ABEH002139 URL: https://ufn.ru/en/articles/1993/3/d/ Citation: Fridman A M, Khoruzhii O V "Nonuniversality of the classical concept of the tangential discontinuity" Phys. Usp.36 (3) 171–176 (1993)