(14)

3α dψ+ 2 (a2 + λ) d( α dψ) = 0,
dλ dλdλ

(15)

and integrating

(a2 + λ)3/2 α dψ= a constant,
dλ

(16)

so that we may put

ψ = ∫ M dλ,
(a2 + λ) P

(17)

P2 = 4 (a2 + λ) (b2 + λ) (c2 + λ),