We discuss the constraints induced by the algebra of the Poincare' generators
on non-relativistic effective field theories. In the first part we derive some
relations among the matching coefficients of the HQET (and NRQCD), which have
been formerly obtained by use of reparametrization invariance. In the second
part we obtain new constraints on the matching coefficients of pNRQCD.Comment: 17 pages, typo in Eq. (97) correcte