Information thread for the Eastern Front

If this thread becomes a sticky, then it is good. Feel free to add weblinks to this topic so future readers are not going to repeat their effort in looking for sources.

The Unknown World War II in the Northern Pacific

Specifically for Fred Wilson's post about fighter planes across Alaska, my memory seems to point out that the documentary The Unknown War mentioned about those flights including a brief -- few minutes -- interview or Q&A with an old Soviet pilot.

The League of Nations compile this demographic and economic information of the Russian Empire and the Soviet Union from late 19th century to beyond the end of ww2