https://en.wikipedia.org/wiki/John_Gall_(author)#Gall's_law
The book is well worth reading.
https://openlibrary.org/books/OL4904457M/Systemantics
(Systemantics is available for borrowing, Systems Bible is not yet, a copy has been sent for digitizing)
Seconded.
Someone once described Systemantics as the book that systwm designers read under the covers at night with a torch.