Some french unit managed to capture one of the hidden hoards of documents from the Messerschmitt Obermaggau R&D center. Evidently they arrived to the place it was hidden (a barn?) before the US, some 20000 pages of documents were all hauled off to Paris, photographed, and then given to the US.

Le Fana has published quite a bit of Messerschmitt stuff over the years taken from some French archive, and it is possible that those documents are from the above haul.