Platt Parmele, Mary.” Primitive conditions and races”, “Slavonic religious and political systems”, “Russians conversion-Greek and latin christianity”, “Principalities-Expansion northward” y “German invasion-Mongol invasion”, en A short history of Russia, Medellin, Cap. I, II, IV, V y VI, págs. 10-13, págs. 13-15, págs. 19-22, págs. 22-24 y págs. 24-28.