Aspects of reduction and transformation of Lagrangian systems with   symmetry
  This paper contains results on geometric Routh reduction and it is a continuation of a previous paper where a new class of transformations is introduced between Lagrangian systems obtained after Routh reduction. In general, these reduced Lagrangian systems have magnetic force terms and are singular in the sense that the Lagrangian does not depend on some velocity components. The main purpose of this paper is to show that the Routh reduction process itself is entirely captured by the application of such a new transformation on the initial Lagrangian system with symmetry. 
E. Garc\'ia-Tora\~no Andr\'es, B. Langerock, F. Cantrijn
math-ph math.MP