Volga

  Stafengagen, Ivan Ivanovich (1728-1784).     Geographical description of the Volga River from Tver to Dmitrevsk for her Imperial Majesty's journey along this river.
[Sankt Petersburg]: With the Imp. Acad. Sciences, [1767].

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Bogolyubov, Nikolai Petrovich (1820-1898). The Volga is from Tver to Astrakhan. St. Petersburg: "Aircraft" Island, 1862.

ПБ