https://www.scirp.org/reference/ReferencesPapers?ReferenceID=2382477
Tchofo-Dinda, P., Moubissi, A.B. and Nakkeeran, K. (2001) Collective Variable Theory for Optical...
Tchofo-Dinda, P., Moubissi, A.B. and Nakkeeran, K. (2001) Collective Variable Theory for Optical Solitons in Fibers. Physical Review E, 64, 016608.