Frequency spectrum of ζ = sin(I/ 2)exp(ıΩ) from a 10 Myr numerical orbital integration of (291) Alice. The abscissa is the frequency ν in arcseconds per year, and the ordinate in amplitude of the quasiperiodic approximation of ζ with Aexp [ı(νt + φ)]. The principal spectral lines are labeled with the standard notation in planetary studies: (i) s is the proper frequency; (ii) s₆ is the principal planetary frequency due to the nodal precession of Saturn; (iii) s₄, s₇ and s₈ are planetary frequencies with smaller amplitudes; and (iv) s ± (g−g₆) are smaller nonlinear terms that also combine the perihelion proper and forced frequencies (due to the proximity of the ν₆ secular resonance at the bottom of the main asteroid belt).