Dodd, R. K.; Bullough, R. K. (4 February 1977). "Polynomial Conserved Densities for the Sine-Gordon Equations". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 352 (1671). The Royal Society: 481–503.
Bibcode:
1977RSPSA.352..481D.
doi:
10.1098/rspa.1977.0012.
ISSN1364-5021.
S2CID123071322.