Reply To: The Library
Reading “The Codebreakers”, mentioned in post #98506, Chapter 12 describes the work of William F. Friedman. Friedman did most of the teaching of class of Army officers, sent in the fall of 1917 to Riverbank’s Department of Ciphers to learn cryptology. The collection of his technical monographs, known as the Riverbank Publications,produced to support the course, are available at the following link:
William F. friedman Collection
This site includes the following classic publications; “The Index of Coincidence and Its Applications In Cryptanalysis” and “A Method for Reconstructing a Primary Alphabet from any One of the Secondary Alphabets” plus many other fascinating documents.