Integrability of Kersten-Krasil'shchik coupled KdV-mKdV equations:   singularity analysis and Lax pair
  The integrability of a coupled KdV-mKdV system is tested by means of singularity analysis. The true Lax pair associated with this system is obtained by the use of prolongation technique. 
A Karasu (Kalkanli), S Yu Sakovich, I Yurdusen