These correspondence courses were great, I miss them. Did several. I have not seen them on PDF before, did you come by a library list? I have my old textbooks someplace in storage. Occasionally I see one the coarse books in a second hand store, I recommend anyone read them as you can find any topic from brick laying to fine grade finish turning of hard materials in the right book, For instance there are several specialty courses from this source rating specific to turning, mill operation, grinding, pump shaft repairs etc. Good find I look forward to reading it.