Information from the following sources was used for this section.
SRH-366 History of Army Strip Cipher – National Archives and Records Administration, NSA
National Cryptographic Museum Online Collection – National Cryptologic Museum, NSA
Six Lectures on Cryptology, Friedman, William F. – Declassified documents, NSA
Parker Hitt’s First Cylinder Device and the Genesis of U.S. Army Cylinder and Strip Devices – Smoot, Betsy Rohaly (Cryptologia, 39:4)
Jefferson Wheel Cypher – CipherHistory.com
CSP-488 Presentation – Maritime.org
Instructions for the cylindrical cipher device (CP-488) – Maritime.org
William Friedman Proposal for Modifying Cipher Device M-94 – Declassified documents, NSA
The Codebreakers: The Story of Secret Writing, 1967 (rev. ed., 1996) – Kahn, David