A: Paris, Île-de-France, France
About 1150 Scholastic theologian Petrus Lombardus (Peter Lombard) of Notre Dame de Paris wrote Libri Quattuor Sententiarum (The Four Books of Sentences).
"The margins of manuscripts and early printed texts in theology, law, and medicine swarm with glosses which, like the historian's footnote, enable the reader to work backward from the finished argument to the texts it rests on. Peter Lombard, the theologian whose commentaries on the Psalms and the Letters of Paul 'are probably the most highly developed of glossed books,' systematically named his sources in marginal glosses, creating what Malcolm Parkes has called, 'the ancestor of the modern scholarly apparatus of footnotes.' Peter certainly deserves credit for one typically modern feat: provoking the first controversy over a wrong reference in a note. One of his glosses mentioned St. Jerome as a source for the story, a popular one in the twelfth century, that the Salome mentioned in the Gospel of Mark was not a woman but the third husband of St. Anne. His student Herbert of Bosham, who attacked this thesis, argued fiercely that Peter's gloss was wrong. As a good pupil, though he preferred to ascribe the mistake to an ignorant scribe rather than his learned teacher. Experimentation with new and safer forms of reference began early: the thirteenth century encyclopedist Vincent of Beauvais tried to avoid scribal errors by incorporating his source references into his texts, presumably on the theory that glosses were more vulnerable than the text proper to errors in copying" (Grafton, The Footnote: A Curious History  30-31).