1. C.R. Hagen, Scale and conformal transformations in galilean-covariant field theory, Phys. Rev. D5 (1972) 377 [ SPIRES ].
2. U. Niederer, The maximal kinematical invariance group of the free Schrödinger equation, Helv. Phys. Acta 45 (1972) 802 [ SPIRES ].
3. M. Henkel, Schrödinger invariance in strongly anisotropic critical systems, J. Stat. Phys. 75 (1994) 1023 [ hep-th/9310081 ] [ SPIRES ].
4. Y. Nishida and D.T. Son, Nonrelativistic conformal field theories, Phys. Rev. D 76 (2007) 086004 [ arXiv:0706.3746 ] [ SPIRES ].
5. J. Negro, M.A. del Olmo, and A. Rodríguez-Marco, Non-relativistic conformal groups I, J. Math. Phys. 38 (1997) 3786.