(la) John Wallis, Arithmetica infinitorum, 1655, Prop. 191.
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« Unfortunately, Wallis' s efforts to reconstruct Brouncker's argument do not take us very far […] Wallis had explained what Brouncker had set out to do, but not why; what he had achieved but not how. » : (en) Jacqueline Stedall, A Discourse Concerning Algebra : English Algebra to 1685, OUP, , 294 p. (ISBN978-0-19-852495-3, lire en ligne), p. 187-188.