One considers representation of cubic polynomials in several variables as the sum of values of univariate polynomials taken at linear combinations of the variables.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-cm92-1-6, author = {A. Schinzel}, title = {On a decomposition of polynomials in several variables, II}, journal = {Colloquium Mathematicae}, volume = {91}, year = {2002}, pages = {67-79}, zbl = {0987.12001}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm92-1-6} }
A. Schinzel. On a decomposition of polynomials in several variables, II. Colloquium Mathematicae, Tome 91 (2002) pp. 67-79. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm92-1-6/