The following is an article about the person who managed Wright Field technical files through 1956. In it, you will mostly see references to American work, and one photo of an early American design that if repainted and the wheel spats removed, looks quite modern. Further reading mentions reports related to German work, and how the files changed hands as they grew very large and cumbersome. The bottom of the article, marked "Footnotes" (put on your reading glasses), provides a few more clues.
http://www.aahs-online.org/articles/Sarah_Clark.php
Hope this helps,
Ed