Downloaded from:

<https://archive.org/details/gnupg-1.4.23-for-dos>
<https://www.gnupg.org/gph/en/manual.html>
<http://pgpkeys.org/docs/7.0/IntroToCrypto.pdf>

See also:

* Older DOS port of GnuPG:

<https://web.archive.org/web/20060205024206/
http://www.caddit.net/php/download.php?file=dg-gnupg.zip>

* Extended version of PGP, includes pgp_dos.exe (16-bit):

<http://lukatela.com/hrvoje/pgp263iamulti06/download.html>