“…It can be checked that l 0 (β, s, Y ) < l 0 ( β, s, Y ) for β = β. It can be thus seen that the problem of computing the ML estimator of (β, s) reduces to finding the maximizer of l(s, Y ) := − log |Σ(s)| − Y ′ R(s)Y over s ∈ S, which we will refer to as the ML estimator of s, compare [11, p. 230] and [4,284]. It can be also observed that for a given value y of the vector Y the ML estimate of s exists if and only if the ML estimate of (β, s) exists.…”