@article {MATHEDUC.02365361,
author = {He, Tian-Xiao and Sinkala, Zachariah and Zha, Xiaoya},
title = {If $F(x) = \int _{x}^{2x} f(t) \, \mathrm{dt}$ is constant, must $f(t)=c/t$?},
year = {2005},
journal = {The College Mathematics Journal},
volume = {36},
number = {3},
issn = {0746-8342},
pages = {199-204},
publisher = {Mathematical Association of America (MAA), Washington, D.C.},
doi = {10.2307/30044852},
abstract = {There are examples showing that the answer is "no".},
msc2010 = {I55xx},
identifier = {2005e.02412},
}