Calin Popescu. Problem 11012. The American Mathematical Monthly, 110(5):438, 2003. [doi]
@article{Popescu03-1, title = {Problem 11012}, author = {Calin Popescu}, year = {2003}, url = {http://www.jstor.org/stable/3647832}, researchr = {https://researchr.org/publication/Popescu03-1}, cites = {0}, citedby = {0}, journal = {The American Mathematical Monthly}, volume = {110}, number = {5}, pages = {438}, }