Bondarenko, A.; Zavgorodniy, A.; Lotnik, D.; Obolenskii, M.; Vovk, R.; Biletskiy, Y. Creep and Depinning of Vortices in Nontwinned YBa₂Cu₃O_6.87 Single Crystal. Fiz. Nizk. Temp. 2008, 34, 645-652.