At the international conference on 'Harmonic Analysis and Integral
Transforms', conducted by one of the authors at the Mathematical
Research Institute in Oberwolfach (Black Forest) in August 1965, it was
felt that there was a real need for a book on Fourier analysis stressing
(i) parallel treatment of Fourier series and Fourier trans- forms from a
transform point of view, (ii) treatment of Fourier transforms in
LP(lRn)_ space not only for p = 1 and p = 2, (iii) classical solution
of partial differential equations with completely rigorous proofs, (iv)
theory of singular integrals of convolu- tion type, (v) applications to
approximation theory including saturation theory, (vi) multiplier
theory, (vii) Hilbert transforms, Riesz fractional integrals, Bessel
potentials, (viii) Fourier transform methods on locally compact groups.
This study aims to consider these aspects, presenting a systematic
treatment of Fourier analysis on the circle as well as on the infinite
line, and of those areas of approximation theory which are in some way
or other related thereto. A second volume is in preparation which goes
beyond the one-dimensional theory presented here to cover the subject
for functions of several variables. Approximately a half of this first
volume deals with the theories of Fourier series and of Fourier
integrals from a transform point of view.