"Regularity and symmetries of nonholonomic systems"

Lagrangian systems with nonholonomic constraints may be considered
as singular differential equations defined by some constraints and
some multipliers.  The geometry, solutions, symmetries and
constants of motion of such equations are studied within the
framework of linearly singular differential equations.  Some
examples are given;  in particular the well-known singular
lagrangian of the relativistic particle, which with the nonholonomic
constraint v^2=c^2 yields a regular system.