I would like to acknowledge the help and support of a number of people
and institutions. Foremost among these must be D.S. Ornstein, as all the
ideas developed here simply generalize his groundbreaking work. I also
though must mention A. Del Junco, J. Feldman, A. Fieldsteel, N. Friedman,
H. Furstenberg, A. Katok, Y. Katznelson, J.P. Thouvenot and B. Weiss as
having contributed significantly, either in conversations or through their
written work, to the development of the ideas presented here.
I want to thank SUNY Albany for sponsoring and supporting a workshop
on this material in the spring of 1983, and the Mathematical Sciences
Research Institute at Berkeley for its support during the fall of 1983.
I also would like to express my appreciation to J. Slack and N. Zanoyan
for their skill and patience in preparing the manuscript.