I did quite a bit of work on the 1940 census indexing project and supervised 30 or so people in their efforts. Never in any educational material I received or any online instruction that I received in order to index was I told to use the 1930 census as a guide. Those that did that were working on their own. The only outside material I used was an atlas to find the counties that certain cities were in. Some people also Googled to find counties. In general, other sources were not to be used in the indexing project, to my knowledge. Sincerely, Holly Bell