Equation Icon  1 1 12 22 1 13 Δ = ¯Δ + ξ + --¯ (ξ − ξ ) − ¯ρξ ξ + ..., 2 Δ ψ = ¯ψ + ξ2 + -1ξ1ξ2 − -1-ξ2ξ3 + ..., Δ¯ 2ρ¯ 3 (3.54 ) ρ = ¯ρ + ξ + ..., σ = ¯σ + ξ4 + -1--(ξ12 + ξ22) +--a--ξ32 + ... 4b¯Δ 4bρ¯2