1. Baikoussis C., Blair D. E.: On Legendre curves in contact 3-manifolds. Geom. Dedicata 49, 135–142 (1994)
2. Balmuş A.: On the biharmonic curves of the Euclidian and Berger 3-dimensional spheres. Sci. Ann. Univ. Agric. Sci. Vet. Med. 47, 87–96 (2004)
3. Balmuş A., Oniciuc C.: Some remarks on the biharmonic submanifolds of S 3 and their stability. An. Stiint. Univ. Al. I. Cuza Iasi, Mat. (N.S.) 51, 171–190 (2005)
4. M. Belkhelfa, F. Dillen and J. Inoguchi, Surfaces with parallel second fundamental form in Bianchi-Cartan-Vranceanu spaces, PDE’s, Submanifolds and Affine Differential Geometry (Warsaw, 2000), 67–87, Banach Center Publ. 57, Polish Acad. Sci., Warsaw, 2002, pp. 67–87.
5. L. Bianchi, Memorie di Matematica e di Fisica della Societa Italiana delle Scienze, Serie Tereza, Tomo XI (1898), 267–352. English Translation: On the three-dimensional spacse which admit a continuous group of motions, General Relativity and Gravitation 33 (2001), no. 12, 2171–2252.