NYPL brings to my attention that the US 1940 Census is online at http://1940census.archives.gov/ and they recommend you use their (NYC) phone book at directme.nypl.org to lookup the address for the name of the person you're looking for. I didn't find any lambiln in Manhattan or Brooklyn and then I stopped; There was a whole page of Rosen though. A full page seemed notable.
Then randomly trying to find one person by address in the census to match up with the name in the book, I started to find this kind of frustrating. It might benefit from some kind of http://www.google.com/recaptcha styled crowd-sourced OCR.
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