The publication of Oberwolfach conference books was initiated by
Birkhauser Publishers in 1964 with the proceedings of the conference 'On
Approximation Theory', conducted by P. L. Butzer (Aachen) and J.
Korevaar (Amsterdam). Since that auspicious beginning, others of the
Oberwolfach proceedings have appeared in Birkhauser's ISNM series. The
present volume is the fifth * edited at Aachen in collaboration with an
external institution. It once again ad- dresses itself to the most
recent results on approximation and operator theory, and includes 47 of
the 48 lectures presented at Oberwolfach, as well as five articles
subsequently submitted by V. A. Baskakov (Moscow), H. Esser (Aachen), G.
Lumer (Mons), E. L. Stark (Aachen) and P. M. Tamrazov (Kiev). In
addition, there is a section devoted to new and unsolved problems, based
upon two special problem sessions augmented by later communications from
the participants. Corresponding to the nature of the conference, the aim
of the organizers was to solicit both specialized and survey papers,
ranging in the broad area of classical and functional analysis, from
approximation and interpolation theory to Fourier and harmonic analysis,
and to the theory of function spaces and operators. The papers were
supplemented by lectures on fields represented for the first time in our
series of Oberwolfach Conferences, so for example, complex function
theory or probability and sampling theory.