Petravchuk, A. P. “On the Sum of an Almost Abelian Lie Algebra and a Lie Algebra Finite-Dimensional over Its Center”.
Ukrains’kyi Matematychnyi Zhurnal, vol. 51, no. 5, May 1999, pp. 636–644,
https://umj.imath.kiev.ua/index.php/umj/article/view/4650.