Higher Order Riesz Transforms for Laguerre Expansions
  In this paper we investigate Lp-boundedness properties for the higher order Riesz transforms associated with Laguerre operators. Also we prove that the k-th Riesz transform is a principal value singular integral operator (modulus a constant times of the function when k is even). To establish our results we exploit a new identity connecting Riesz transforms in the Hermite and Laguerre settings. 
Jorge J. Betancor, Juan C. Fari\~na, Lourdes Rodriguez-Mesa, Alejandro   Sanabria-Garcia