@online{MathMagic,
title = {Math Magic},
author = {Erich Friedman},
url = {http://www2.stetson.edu/{\~{}}efriedma/mathmagic/},
urldate = {2017-06-21},
abstract = {Math Magic is a web site devoted to original mathematical recreations.},
comment = {A monthly recreational maths problem, stretching back to 1998.},
year = 1998,
collections = {puzzles}
}