Isometry groups of Lobachevskian spaces, similarity transformation groups of Euclidean spaces and Lorentzian holonomy groups

In the present paper transitively and simply transitively acting isometry groups of Lobachevskian spaces and transitively acting similarity transformation groups of Euclidean spaces are classified. A geometrical proof of the result of L. Berard Bergery and A. Ikemakhen about the classification of weakly-irreducible not irreducible subalgebras of $so(1,n+1)$ is given.