O. Kowalski et Z. Vlasek, CLASSIFICATION OF RIEMANNIAN 3-MANIFOLDS WITH DISTINCT CONSTANT PRINCIPAL RICCI CURVATURES, Bulletin of the Belgian Mathematical Society Simon Stevin, 5(1), 1998, pp. 59-68
We prove that the local isometry classes of Riemannian 3-manifolds wit
h distinct constant Ricci eigenvalues are parametrized by three arbitr
ary functions of two variables. This improves essentially the earlier
result by A.Spiro and F.Tricerri from [9].