https://www.cambridge.org/core/journals/mathematical-gazette/article/abs/593-the-irrationality-of-2/18BADD0AB7114F1809B9F3EF6F82D20F https://www.cambridge.org/c

https://www.cambridge.org/core/journals/mathematical-gazette/article/abs/593-the-irrationality-of-2/18BADD0AB7114F1809B9F3EF6F82D20F https://www.cambridge.org/core/journals/mathematical-gazette... https://en.wikipedia.org/wiki/Theodor_Estermann https://en.wikipedia.org/wiki/Theodor_Estermann