The book, Instrumentation Training Course: Pneumatic Instruments Vol 1, (brown paperback cover) published by Howard Sams and copyrighted in 1968 has a 3 page chapter on the Foxboro controller. But it assumens that the reader understands what a true force balance controller is; that topic along with other pneumatic fundamentals, having been covered in earlier sections.
Copies routinely show up on the used book sites for $1.00 plus postage.
If you go to look for it, make sure it's pneumatic, Vol 1, because the same title had subtitle Vol 1: Electronic Instruments with the green cover.