From the materials of the Smolensk local historian V.K.Efremenkova.(On the 100th anniversary of N.V. Dobrovolsky).

From the materials of the Smolensk local historian V.K.Efremenkova.(On the 100th anniversary of N.V. Dobrovolsky).- -.-Agreement No. 24 of 02/12/2016 category 38 manuscript of the works of members of the Russian Geographical Society and separate documents in the Smolensk province, case 38..Electronic copy source: PB