@article{VM_2003_5_1_a2,
     author = {Jay Kappraff and Gary W. Adamson},
     title = {A {Unified} {Theory} of {Proportion}},
     journal = {Visual Mathematics},
     publisher = {mathdoc},
     volume = {5},
     number = {1},
     year = {2003},
     url = {http://geodesic.mathdoc.fr/item/VM_2003_5_1_a2/}
}