and s ≤ θ ≤ t. The dot notation is qt,s x,y (θ) = d dθ q t,s x,y (θ). For the variable p a similar paths can be defined; Θ ∆ , p ∆ (p (0) , p (1) , . . . , p (ν-1) , p) . Note p = p (ν) . Like with x the employment of the symbolism will be convenient for the presentation. When necessary the index ν will be used.