Wikipedia references are notoriously unreliable. I have encountered authors’ names misspelled, and once a book that didn’t even exist (although that has since been removed). Anyway, I have been trying to authenticate a book referenced in the Wikipedia article on the Second Council of Lyons (1274). I made an exhaustive search for it on Abebooks but came up with nothing, and there is no copy in Google Books either. The book is entitled: “The Byzantine Reaction to the Second Council of Lyons, 1274,” by eminent Byzantinist Donald MacGillivray Nicol, published in 1971. It might not even be a book; perhaps just a chapter in another book on the subject of the Crusades, or the union of the churches. I just can’t know. If anybody more skilled at this sort of thing can offer their assistance, I would be very much obliged.