NSA Museum Library has provided "Hagelin M-209 Cryptanalysis from
   Ciphertext Alone,"
   Reeds, Ritchie, Morris, 1978.
   [1]https://cryptome.org/2015/12/ReedsTheHagelinCipherBellLabs1978.pdf
   NSA would not release it under FOIA, claiming it was a private paper.
   Back story:
   [2]http://bell-labs.com/usr/dmr/www/crypt.html

References

   1. https://t.co/MbE5UNMtzb
   2. http://bell-labs.com/usr/dmr/www/crypt.html