There is a known expression for a solution which is an N -soliton solution, which at late times resolves into N separate single solitons. The solution depends on an decreasing positive set of parameters χ χ 1 , ⋯ ⋯ , χ χ N > 0 and a non-zero set of parameters β β 1 , ⋯ ⋯ , β β N . The solution is given in the form ϕ ϕ ( x , t ) = − − 2 ∂ ∂ 2 ∂ ∂ x 2 l o g [ d e t A ( x , t ) ] where the components of the matrix A ( x , t ) are given by A n m ( x , t ) = δ δ n m + β β n e 8 χ χ n 3 t e − − ( χ χ n + χ χ m ) x χ χ n + χ χ m .