Factorization of linear and nonlinear differential operators: necessary   and sufficient conditions
  An algebraic approach for factorizing nonlinear partial differential equations (PDEs) and systems of PDEs is provided.   In the particular case of second order linear and nonlinear PDEs and systems of PDEs, necessary and sufficient conditions of factorization are given. 
Mahouton Norbert Hounkonnou and Pascal Dkengne Sielenou
math.AP