Weronika Buczyńska, Jarosław Buczyński, Johannes Kleppe, and Zach Teitler. Apolarity and direct sum decomposability of polynomials. Michigan Math. J. 64 (2015), no. 4, 675-719
arXiv:
https://arxiv.org/abs/1307.3314
doi:
10.1307/mmj/1447878029