Rational Bundles and Recursion Operators for Integrable Equations on   A.III-type Symmetric Spaces
  We analyze and compare the methods of construction of the recursion operators for a special class of integrable nonlinear differential equations related to A.III-type symmetric spaces in Cartan's classification and having additional reductions. 
Vladimir S. Gerdjikov, Georgi G. Grahovski, Alexander V. Mikhailov,   Tihomir I. Valchev
nlin.SI math-ph math.MP