This is a comment about the PDF you linked. The “queue” example presented early in this lecture is a bastardized version of the same example from “The Craft of Prolog” by Richard O’Keefe, without attribution. Using a “difference list” like that to implement a queue certainly predates both, but the way the text is written (order of examples, considerations, improvements and so on) is copied 1:1. The text and code are re-written though.