Mathematical wrinkles for teachers and private learners .. (1912)
Jones, Samuel I. (Samuel Isaac), b. 1880 · Gunter, Tex., S.I. Jones · leaf 109
the reader that the result is true. Let A, B, 0 be three contiguous districts, and let X be any other district contiguous with all of them. Then X must lie either wholly outside the external boundary of the area ABC or wholly inside the internal boundary; that is, it must occupy a position either… … ble case is that already treated. Moreover, any of the above areas may diminish to a point and finally disappear without affecting the argument. That we may require at least four coloi;s is obvious from.
Mathematics · Mathematical recreations
Internet Archive · Cornell University Library · Public domain (published before 1931). Free to use for anything.
![An illustration from Optical illusions of motion [electronic resource] (1882)](https://img.insideoutlibrary.com/img/200/ia-b21642710-62-0.webp)
