Fig. Explanation of the used symbols in equations ( ) and ( ). Reprinted with permission from the work of Roth et al. and if ω ∈ R, then both roots lie exactly on a unit circle |z-| = |z+| = 1. However, if we consider a limit ω → ω + i0, then we can notice that zalways lies within the unit circle, whereas z+ is placed outside. Therefore