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5. D'yachenko, N. (1908). Torgovlya Rossii s Bolgariey. Donesenie sekretarya diplomati cheskogo agentstva v Sofii [Trade between Russia and Bulgaria. Report of the secretary of the dip lomatic agency in Sofia] in Sbornik konsul'skikh doneseniy za 1907 g., V, 383-403. (in Russian).