J.A. Sanders, J.P. Wang, Lecture Notes in Physics, 767, Integrability, 2009, 89
Guha P., “Euler-Poincaré formalism of (two component) Degasperis–Procesi and Holm–Staley type systems”, J. Nonlinear Math. Phys., 14:3 (2007), 390–421
Hone A.N.W., Novikov V.S., “On a functional equation related to the intermediate long wave equation”, J. Phys. A, 37:32 (2004), L399–L406