“…Corresponding classes of groups were studied by Baumeister ( [1]), who showed, in particular, that any group in MA is solvable, and that a group belongs to MD if and only if it is solvable. Similar problems concerning factorisations of Lie algebras as sums of subalgebras of a certain type have been studied extensively (see, for example, [12], [13], [2], [9], [17], [19], [20], [21] and the references contained therein. )…”