[1] ANDĚL J.: Statistical Analysis of Time Series. SNTL, Prague 1976 (in Czech).
[2] GOCHBERO J. C., KREJN M. G.: Introduction to Theory of Linear Non-self-adjoint Operators in Hilbert Space. Nauka, Moskva 1965 (in Russian).
[3] MELNICHENKO G.: Linear transformations of random processes. in: Statistical Problem of Control 56, Institute of Mathematics and Cybernetics, Vilnius 1982, 31-44 (in Russian).
[4] NIEMI H.:
On the linear prediction problem of certain nonstationary stoohastio processes. Math. Scand. 39 (1976), 146-160.
MR 0426128
[5] NIEMI H.:
On the effect of a nonstationary noise on ARMA models. Scand. J. Statist. 10 (1983), 11-17.
MR 0711330
[7] TJØSTHEIM D., THOMAS J.B.:
Some properties and examples of random processes that are almost wide sense stationary. IEEE Trans. Inf. Theory 21 (1975), 257-262.
MR 0386004
[8] TYSSEDAL J., TJØSTHEIM D.:
Autoregressive processes with a time dependent variance. J. Time Series Analysis 3 (1982), 209-217.
MR 0695232