Berry, M. V.; Tabor, M. (1977-09-15). "Level clustering in the regular spectrum". Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences. 356 (1686): 375–394. Bibcode:1977RSPSA.356..375B. doi:10.1098/rspa.1977.0140. ISSN0080-4630.
Berry, M. V.; Tabor, M. (1977-09-15). "Level clustering in the regular spectrum". Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences. 356 (1686): 375–394. Bibcode:1977RSPSA.356..375B. doi:10.1098/rspa.1977.0140. ISSN0080-4630.
Berry, M. V.; Tabor, M. (1977-09-15). "Level clustering in the regular spectrum". Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences. 356 (1686): 375–394. Bibcode:1977RSPSA.356..375B. doi:10.1098/rspa.1977.0140. ISSN0080-4630.