참고문헌
- Rational quadratic forms J. W. S. Cassels
- Nagoya Math. J. v.140 Rank 2 symmetric hyperbolic Kac-Moody algebras S.-J. Kang;D. J. Melville
- Introduction to number theory L. K. Hua
- Atti Dell' Accademia Pontificia De' Nouvi Lincei v.19 M. C. Richaud