[1] J. Michálek:
Locally stationary covariances. In: Trans. Tenth Prague Conf. on Inform. Theory, Statist. Dec. Funct. Random Processes, Academia, Prague 1987.
MR 1136266
[2] J. Michálek:
Random sequences with normal covariances. Kybernetika 23 (1986), 6, 443-457.
MR 0922621
[3] R. A. Silverman:
Locally stationary random processes. IRE Trans. Inform. Theory IT-3 (1957), 3, 182-187.
MR 0090931