“…Proof: Throughout this proof, we use V σ(t) (t) to denote V σ(t) (t, x σ(t) (t)) for simplicity. Assuming a certain switching sequence on (t 0 , t f ] to be t 1 , t 2 , ..., t k , ..., k ≤ N (t 0 , t f ), then by integrating (15) on both sides from t 0 to t k+1 , and applying (16), one obtains…”