Johnson定理

參考資料:
Roger A. Johnson, Advanced Euclidean Geometry, Dover, p. 75.
Martin Gardner,
Knotted Doughnuts and Other Mathematical Entertainments, pp. 164-185, p. 191.
Harley Flanders, Concurrent Circles of Equal Radii, Math Gazette, 56 (1972), pp. 126-127.
岩田至康,幾何學大辭典, Vol. 4, 265-266.
Roger A. Johnson, A Circle Theorem, Amer. Math. Monthly, Vol 23 (1916), p. 161.
GSP網頁

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