Automorphism group of a toric variety

We calculate the automorphism group of a complete toric variety $X$ with torus $T_M$. We prove that the radical unipotent of $Aut_k^0X$ is a semidirect product of additive groups, the reductive part is a quotient of a product of lineal groups and we give the action of linear groups on the additive groups. We also prove that $Aut_kX/Aut_k^0X$ is a quotient of the group of automorphisms of $M$ leaving invariant the fan.