Notes on the theory and application of Fourier transforms. I, II
R. E. A. C. Paley, Norbert Wiener · Transactions of the American Mathematical Society · 1933
where B is a constant which may depend on f(x). We say that the class CA is quasi-analytic if a function of CA is defined completely over (o, co) by the values of its derivatives f(P)(x) (v =0, 1, 2, ) at a single point xo, or, what is the same thing, if the equations f(v)(xo) =0 (v=O,1,2, ) together with the condition f(x) c CA, imply that f(x) vanishes identically. The theorem is the following: