Matthias Beck, Marcin Mazur, Shelemyahu Zacks. Problem 11048. The American Mathematical Monthly, 110(10):956, 2003. [doi]
@article{BeckMZ03,
title = {Problem 11048},
author = {Matthias Beck and Marcin Mazur and Shelemyahu Zacks},
year = {2003},
url = {http://www.jstor.org/stable/3647971},
researchr = {https://researchr.org/publication/BeckMZ03},
cites = {0},
citedby = {0},
journal = {The American Mathematical Monthly},
volume = {110},
number = {10},
pages = {956},
}