“…Although significant progress in the understanding of the behavior of numerical methods for Helmholtz problems has been made in the past, a general, full analysis that is explicit in the wave number k and discretization parameters is still not available. Partial results such as sharp estimates for the inf-sup constant of the continuous equations, lower estimates for the convergence rates, one-dimensional analysis by using the discrete Green's function as well as a dispersion analysis for finite element discretizations and generalizations thereof have been derived by many researchers in the past decades (see, e.g., [2,4,6,7,9,10,11,15,17,18,19,22,23,24,25,26,27,28,33,38,43,44]). …”