1. Brown, H., Bülow, R., Neubüser, J., Wondratschek, H., Zassenhaus, H.: Crystallographic Groups of Four-Dimensional Space. Wiley Monographs in Crystallography. Wiley, New York (1978)
2. Cassels, J.W.S.: Rational Quadratic Forms. Academic Press, London (1978)
3. Conway, J.H. assisted by Fung, F.Y.C.: The Sensual (Quadratic) Form. Carus Mathematical Monographs, vol. 26. MAA, Washington (1977)
4. Conway, J.H., Sloane, N.J.A.: On the classification of integral quadratic forms. In: Conway, J.H., Sloane, N.J.A. (eds.) Sphere Packings, Lattices and Groups, 3rd edn. Springer, Berlin (1998)
5. Dickson, L.E.: Studies in the Theory of Numbers. Chelsea Publishing Company, New York (1957)