1. Adler, R., Bazin, M. and Schiffer, M. (1965).Introduction to General Relativity, (McGraw-Hill, New York).
2. du Plessis, J.C. (1969). Tensorial Concomitants and Conservation Laws,Tensor (N.S.),20 347?360.
3. Horndeski, G. and Lovelock, D. (1972). Scalar Tensor Field Theories,Tensor (N.S.),24, 79?92.
4. Horndeski, G. (1972). Dimensionally Dependent Divergencies,Proc. Comb. Phil. Soc.,72, 77?82.
5. Lovelock, D. (1967). The Lanczos Identity and its Generalisations,Atti Accad. Naz. Lincei Rend. Cl. Sci. Fis. Mat. Natur.,42, 187?194.