On UrKdV and UrKP
  We present two extensions of Wilson's explanation of the Miura map from MKdV to KdV. In the first we explain the map of Svinolupov et al from a certain UrKdV-like equation to KdV, and in the second we explain Konopelchenko's map from the modified KP equation to KP. In the course of the latter we introduce an ``UrKP'' system, with an infinite dimensional symmetry, providing us with a systematic method to construct Backlund transformations for the modified KP and KP equations. 
Didier A Depireux and Jeremy Schiff, U de Montreal and Bar Ilan