@article{VM_2007_9_3_a0,
     author = {Paulus Gerdes},
     title = {Mwani {Colour} {Inversion,} {Symmetry} and {Cycle} {Matrices}},
     journal = {Visual Mathematics},
     publisher = {mathdoc},
     volume = {9},
     number = {3},
     year = {2007},
     url = {http://geodesic.mathdoc.fr/item/VM_2007_9_3_a0/}
}