A caution. Most of the examples in his books use papers that no longer exist and prepared toners that no longer exist, still a wonderful book. Kodak printed a beautiful book on Quality printing in black and white that is quite available.
Many materials are sadly gone but as the book (I have a copy from the first edition, but dedicated to yours truly and not for sale) carries recipes for making most from scratch, it's still a treasure trove for anyone interested in chemical toning.