The aim of this paper is to define functions of several commuting and non-commuting sell-adjoint pseudo-differential operators of non-positive order, by means of the H. Weyl formula f(A(1),...,A(r))=1(2 pi)(r/2)/(2 pi)(r/2)integral(Rr) e(i(tlAl+...+trAr))(f) over tilde(t)dt Given 1展开▼
