Controllability of the Laguerre and the Jacobi Equations
  In this paper we study the controllability of the controlled Laguerre equation and the controlled Jacobi equation. For each case, we found conditions which guarantee when such systems are approximately controllable on the interval $[0, t_1]$. Moreover, we show that these systems can never be exactly controllable 
Diomedes Barcenas, Hugo Leiva, Yamilet Quintana and Wilfredo Urbina