Consider the continuous set of functions Φ Φ a ( Γ Γ ) = δ δ ( A ( Γ Γ ) − − a ) = ∏ ∏ n δ δ ( A n ( Γ Γ ) − − a n ) with a = a n constant. Any phase space function G ( A ( Γ Γ ) ) depending on Γ Γ only through A ( Γ Γ ) is a function of the Φ Φ a , namely