The short-range expansion in solid state physics Helge Holden, Raphael Høegh-Krohn, Steinar Johannesen (1984) Annales de l'I.H.P. Physique théorique
Two dimensional lattice vibrations from direct product representations of symmetry groups. Boyd, J.N., Raychowdhury, P.N. (1983) International Journal of Mathematics and Mathematical Sciences