A general but obsolete/withdrawn NIST document that introduced a lot of terms and concepts for “signal” versus “power” grounding is www.itl.nist.gov/fipspubs/fip94.pdf Early on, authors Lewis and Kalbach were thought to have landed from Mars with some very revolutionary but much-needed discussion on “convergence” of the two widely conflicting systems, and—equally important—the modes of thinking that fostered the original confusion.