Stewart, B.M.; Frame, J.S. Solution to advanced problem 3819. American Mathematical Monthly. March 1941, 48 (3): 216–9. JSTOR 2304268. doi:10.2307/2304268.
jstor.org
Stewart, B.M.; Frame, J.S. Solution to advanced problem 3819. American Mathematical Monthly. March 1941, 48 (3): 216–9. JSTOR 2304268. doi:10.2307/2304268.