By definition, 𝜑 E0? > 1 and Py E0? 7 > 0. Thus, from Eqs. (34c, d) and ( ), we have 𝑟 V,E0? < 0 (𝑙 = 1 -3). Therefore, following the methodology in Section 6.3, it can be concluded that the implementation of SAS in the form of Eqs. ( )-( ) is unconditionally stable, since a perturbation on a single value of 𝜁 E0? produces a variation in subsequent values that does not increase step by step, regardless of the value of Δ𝜏 (Gear, 1971).