M.A. Obolenskii, R.V. Vovk, A.V. Bondarenko, and N.N. Chebotaev, Localization effects and pseudogap state in YBa₂Cu₃O_7-d single crystals with different oxygen content: Pseudogap, Low Temp. Phys. 32, (2006) [Fiz. Nizk. Temp. 32, 746-752, (2006)] DOI: https://doi.org/10.1063/1.2215373.