Schwaiger, Jens. “Functional Equations for Homogeneous Polynomials Arising from Multilinear Mappings and Their Stability”. Annales Mathematicae Silesianae, vol. 8, Sept. 1994, pp. 157-71, https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/14232.