Vector colorability
A coloring of a family of vectors is an assignment of a color to each vector so that color classes are linearly independent. The authors define a graph associated with a colored family of vectors. The family is planar if there exists a coloring which yields a planar associated graph. The authors show that a planar family of vectors is 4-colorable. Two proofs are given, one using the 4-color Theorem for graphs, and the other not.
scientific article; zbMATH DE number 4043861