  Let f_1 and f_2 be real analytic germs of independent variables. In this
paper, we assume that f_1, f_2 and f = f_1 + f_2 satisfy a_f -condition. Then
we show that the tubular Milnor fiber of f is homotopy equivalent to the join
of tubular Milnor fibers of f_1 and f_2.
