Gregory Galperin, Hillel Gauchman. Problem 11103. The American Mathematical Monthly, 111(8):724, 2004. [doi]
@article{GalperinG04,
title = {Problem 11103},
author = {Gregory Galperin and Hillel Gauchman},
year = {2004},
url = {http://www.jstor.org/stable/4145048},
researchr = {https://researchr.org/publication/GalperinG04},
cites = {0},
citedby = {0},
journal = {The American Mathematical Monthly},
volume = {111},
number = {8},
pages = {724},
}