“…where ∆ n,k := µ k + µ n−k − µ n + E(T n ). Different approaches have been proposed to the asymptotics of σ 2 n ; these include an elementary induction approach (see [7,52]), the second-moment approach (see [67,69,70,71]), Poissonized variance (by consideringf 2 (z) −f 2 1 (z)) approach (see [59,60,76,93,77,90]), (bivariate) characteristic function approach ( [57,77,60]), and Schachinger's differencing approach [95].…”