Petravchuk , A. P. “Lie Algebras, Expanded into the Sum of Abelian and Nilpotent Subalgebras”. Ukrains’kyi Matematychnyi Zhurnal, vol. 40, no. 3, Apr. 1988, pp. 385-8, https://umj.imath.kiev.ua/index.php/umj/article/view/9153.