Lumped mass approximation for an isoparametric finite element eigenvalue problem

We consider isoparametric variant, of the lumped mass modification of the standard Calerkin method for second-order elliptic eigenvalue prohlem. The lumping of the mass matrix results from the use of an appropriate isoparametric quadrature formula for the integrals over triangular Lagrange finite elements. The analysis of the 7-node finite element transformations is made. The convergence of the eigenvalue approximations is proved.