you people are all talking about the definite integrals where we integrate a function over a defined 2-d region in this case (fubini theorem)..im talking about the indefinite integrals or the integrals like the one in convolution of three signals (functions) ..x(t)*y(t)*z(t).....there the limits are not defined the way we do in fubini theorem to convert a multiple integral into iterated single integrals .....