Help me please to find reference for the proof of the following theorem:
Theorem. Let $\theta$ be a Leibniz cocycle on the Leibniz algebra L with values in $V,$ and assume $\theta^{\bot}\cap C(L)=(0).$ Then the automorphism group $Aut(L_{\theta})$ of the extension algebra $L_{\theta}$ consists of all linear operators of the matrix form
$$
\left[
\begin{array}{lr}
\alpha_0 & 0 \\
\\
\phi & \psi \\
\end{array}
\right],
$$
where $\alpha_0 \in Aut(L), \ \psi = \alpha|{C(L_{\theta})} \in GL(k),$ and $\phi \in Hom(L, V),$ such that $\theta (\alpha_0x, \alpha_0y) = \phi[x,y] + \psi\theta(x,y),$ all $x, y \in L.$
(L, [.,.]) is a Leibniz algebra over F
