A highly surprising message just arrived here at Cipher Mysteries from our Chaocipher Clearing House chum Moshe Rubin:-
Is your readership aware that NSA has placed the entire text [of Mary D’Imperio’s “An Elegant Enigma”] on its site?
I couldn’t find the link on your site so here it is!
This is a great find, highly recommended for all Voynich researchers – if you haven’t read it already, download it straight away! Having said that, even though it took me six attempts to download it completely (doubtless they were tracert’ing me to see if I just happened to be a terrorist, bless ’em), I did get it all in the end. But please let me know if this happens to get removed (which is always possible).
Incidentally, this is just one of a number of cryptological history publications the NSA has kindly made available on its website. The 2007 article by John Clabby on Brigadier John Tiltman (“A Giant Among Cryptanalysts“) is also well worth looking at (though not nearly so essential as D’Imperio, naturally).