1. Mannhart J, Chaudhari P, Dimos D, Tsuei C, McGuire T (1988) Phys.Rev.Lett. 61: 2476
2. Ketchen MB, Kopley T, H. Ling (1984) Appl. Phys. Lett. 44: 1008
3. de Waele ATAM, Smokers RTM, van der Heijden, RW (1987) Phys. Rev. B35, 8858
4. Aminov BA, Borisovskii W, Brandt NB, Muller R, Thu NM, Ponomarev YG, Sudakova MV, Graboi lE, Kaul AR Tretyakov YB (1988) JETP Lett. 47: 675
5. Alvarez G, Taylor KNR, Russell GJ (1989) Physica C. 162–164 1043