I am working on the exact same problem on my 1896 victorian. We are redoing the kitchen and have removed tile, tile subfloor, and linoleum layers... The linoleum's plastic layer pulled up easy with the help of a heat gun, but the paper/adhesive backing is stuck firmly to my 3/8" x 1.5" original oak floors.
So far I have tried WITHOUT success:
*Heat gun + manual sraping
*Spraying an area with H2O+wall paper remover
My adhesive layer is very hard. It doesn't seem to be gooey and anymore, so I am going to try hitting it with a hand sander and hope it doesn't clog the paper. If that works, I could remove most of it with a hand sander (just barely down to the wood surface) and then run a floor sander over the whole room.
My only other idea is to pull the floor up and maybe run each piece through a planer to shave off the glue. The floor has to come up anyway b/c this original oak floor only covers half the room (part of the room is an addition). We are slowly accumulating enough matching salvage material to then re-install this wood on the whole floor.
I have to figure something out soon b/c my wife is already talking about wanting to just bury it under a layer of subfloor and starting over.