Hausdorff measures and the Morse-Sard theorem

Let F: U subset of R-n --> R-m be a differentiable junction and p < m an integer. If k greater than or equal to 1 is an integer, alpha epsilon [0,1] and F epsilon Ck+(alpha), if we set C-p(F) = {x epsilon U / rank(Df(x)) less than or equal to p} then the Hausdorff measure of dimension (p + n-p/k+alpha) of F(C-p(F)) is zero.