A link to a pdf version of “Knowledge of the Holy” can be found here
A link to a hardcopy of the book at Christian Book Distributors can be found here
A link to Tozer’s sermon given in Pittsburgh in 1956 in which he asked prayer of his hearers for the time to write this book can be found here. His request starts about the 14m 44s mark.
A link to the lesson on “Do It Yourself Theology” by Michael Reeves of Theology Network in the United Kingdom can be found here