Sokolov N.A. Report on his trip to the Caucasus in the areas of detailed studies of oil-bearing areas. In Russian (ask us if in doubt)/Sokolov N.A. Otchet o poezdke na Kavkaz v rayony detal'nykh issledovaniy neftenosnykh ploshchadey. St. Petersburg printing house K. Birkkifeld 1901. 575-589 p. SKUalbdf8c356b418b4a98.