Almost inner derivations of some Leibniz algebras

The present paper is devoted to almost inner derivations of thin and solvable Leibniz algebras. Namely, we consider a thin Lie algebra, solvable Lie algebra with nilradical natural graded filifform Lie algebra, natural graded thin Leibniz algebra, thin non-Lie Leibniz algebra and solvable Leibniz algebra with nilradical nul-filiform algebra. We prove that any almost inner derivations of all these algebras are inner derivations.