Nuclear Matrix Elements of $0\nu\beta\beta$-Decay: Possible Test of the   Calculations
  A possible model independent test of the theoretically calculated nuclear matrix elements of $0\nu\beta\beta$-decay is proposed. The test can be accomplished if $0\nu\beta\beta$-decay of three (or more) nuclei is observed. The selection of the nuclei for the next generation of $0\nu\beta\beta$-decay experiments should be done taking into account {\it also} considerations regarding the possibility to test the nuclear matrix element calculations. 
S.M. Bilenky and S.T. Petcov