It is appropriate at this point to interleave citations into the discussion. These have their own fascinating history! In the 19 th and early 20 th century, citations in an article were often sparse and cryptic, with journal references heavily abbreviated, possibly to save typesetting eYort. I cannot resist citing 6 this article by Niels Bohr dating from 1922 as an extreme example. Probably one of the most influential articles of that century -leading to a Nobel prize no less -it contains no citations either as footnotes or endnotes and instead, individuals contributing to the area are acknowledged throughout the text. Nonetheless, by the second half of the 20 th century, most research articles had fully separated citations into a discrete list at the end of the article. Arguably, these lists were often mis-used by inclusion of text-based footnotes extending the discussion of the main body of the article. Individual numbered citations could themselves contain sub-lists of journal references associated by an inferred common theme and of hoped-for relevance to the discussion. Such lists started suYering from the same issues as ESI, in other words an apparently lack of the formal structures and declared semantics so helpful for AI/ML; These will be referred to as unstructured citations for reasons that will shortly become apparent.