“…and Γ p n ðβ, aÞ ⟶ ∞as n ⟶ ∞: The authors in [12] gave the first eigensurface Γ p 1 ð:,aÞ and showed that if a ≥ 0 a.e. in Ω, then Γ p 1 ð:,aÞ is simple (i. e., the associated eigenfunctions are a constant multiple of one another) and principal, i.e., the associated eigenfunction, denoted by φ p,a is positive or negative on Ω with…”