Urkryptografen ("the Clock Cryptograph"). - Niels Faurholt (Cryptologia, 2003)

Julius Petersen - Danish Mathematician and Cryptologist. - Augusto Buonafalce; Niels Faurholt; Bjarne Toft (Cryptologia, 2006)

Alexis Køhl: a Danish Inventor of Cryptosystems. - Niels Faurholt (Cryptologia, 2006)

E.S.Schieber German Code Device from WWII. - Niels Faurholt (Cryptologia, 2010)

Willard's System. - Niels O. Faurholt (HistoCrypt, 2018)