“…Stationarity of J(a) with respect to Q results in a set of linear equations for u(x) PW(x)P'u(x) = P W(X)U, (2.6) with the entries of the matrices P and W given by P,,=JI,(R.,) j=l...., m, iE{l,.... +,(x)X)} (2. 7) w,l = w,w,,, i, j E ( I, . , II 1 W,(X) > 0).…”