Https://upload.wikimedia.org/wikipedia/commons/a/aa/Pacific_Culture_Areas.pngBut maps developed through the sixteenth to 18th hundreds of years tended to differ in how to continue the boundary further than the Don bend at Kalach-na-Donu (in which it is closest to the Volga, now joined with it from the Volga–Don Canal), into territory not explained in any detail http://Cloverjuice.com