@article {MATHEDUC.06132026,
    author       = {Trenkler, G\"otz and Trenkler, Dietrich},
    title        = {The numerical range of the Luoshu is a piece of cake -- almost.},
    year         = {2012},
    journal      = {The College Mathematics Journal},
    volume       = {43},
    number       = {5},
    issn         = {0746-8342},
    pages        = {371-376},
    publisher    = {Mathematical Association of America, Washington, DC},
    doi          = {10.4169/college.math.j.43.5.371},
    abstract     = {Summary: The numerical range, easy to understand but often tedious to compute, provides useful information about a matrix. Here we describe the numerical range of a $3 \times 3$ magic square. Applying our results to one of the most famous of those squares, the Luoshu, it turns out that its numerical range is a piece of cake -- almost.},
    msc2010      = {H65xx (G75xx)},
    identifier   = {2013a.00672},
}