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[2] J. M.  Melenk, I.  Babuška: Approximation with harmonic and generalized harmonic polynomials in the partition of unity method. Comput. Assist. Mech. Eng. Sci. 4 (1997), 607–632.

[3] J. M.  Melenk, I.  Babuška: The partition of unity finite element method: Basic theory and applications. Comput. Methods Appl. Mech. Eng. 139 (1996), 289–314. MR 1426012

[4] I.  Babuška, J. M.  Melenk: The partition of unity method. Int. J. Numer. Methods. Eng. 40 (1997), 727–758. MR 1429534

[5] J. M.  Melenk: On generalized finite element methods. PhD. thesis, University of Maryland, 1995.

[6] I.  Babuška, T.  Strouboulis, and K.  Copps: The design and analysis of the generalized finite element method. Comput. Methods Appl. Mech. Eng. 181 (2000), 43–69. MR 1734667

[7] T.  Strouboulis, I.  Babuška, and K.  Copps: The generalized finite element method: An example of its implementation and illustration of its performance. Int. J.  Numer. Methods Eng. 47 (2000), 1401–1417. MR 1746489

[8] T.  Strouboulis, K.  Copps, and I.  Babuška: The generalized finite element method. Comput. Methods Appl. Mech. Eng. 190 (2001), 4081–4193. MR 1832655

[9] T.  Strouboulis, L.  Zhang, and I.  Babuška: Generalized finite element method using mesh-based handbooks: Application to problem in domains with many voids. Comput. Methods Appl. Mech. Eng. 192 (2003), 3109–3161. MR 2007029

[10] T.  Strouboulis, L.  Zhang, and I.  Babuška: $p$-version of the generalized FEM using mesh-based handbooks with applications to multiscale problems. Int. J.  Numer. Methods Eng. 60 (2004), 1639–1672. MR 2069141

[11] N.  Sukumar, D. L.  Chopp, N.  Moës, and T.  Belytschko: Modeling holes and inclusions by level sets in the extended finite element method. Comput. Methods Appl. Mech. Eng. 190 (2001), 6183–6200. MR 1857695

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[14] R.  Sugimoto, P.  Bettess, and J.  Trevelyan: A numerical integration scheme for special quadrilateral finite elements for the Helmholtz equation. Commun. Numer. Methods Eng. 19 (2003), 233–245. MR 1965603

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[17] P.  Ortiz, E.  Sanchez: An improved partition of unity finite element model for diffraction problems. Int. J.  Numer. Methods Eng. 50 (2001), 2727–2740.

[18] P.  Ortiz: Finite elements using a plane-wave basis for scattering of surface water waves. Philos. Trans. R.  Soc. Lond . A 362 (2004), 525–540. MR 2075905 | Zbl 1083.76045

[19] C.  Farhat, I.  Harari, and L. P.  Franca: The discontinuous enrichment method. Comput. Methods Appl. Mech. Eng. 190 (2001), 6455–6479. MR 1870426

[20] C.  Farhat, I.  Harari, and U.  Hetmaniuk: A discontinuous Galerkin method with Lagrange multipliers for the solution of Helmholtz problems in the mid-frequency regime. Comput. Methods Appl. Mech. Eng. 192 (2003), 1389–1419. MR 1963058

[21] P.  Rouch, P.  Ladevèze: The variational theory of complex rays: A predictive tool for medium-frequency vibrations. Comput. Methods Appl. Mech. Eng. 192 (2003), 3301–3315.

[22] H.  Riou, P.  Ladevèze, and P.  Rouch: Extension of the variational theory of complex rays to shells for medium-freqency vibrations. J.  Sound Vib. 272 (2004), 341–360.

[23] P.  Ladevèze, H.  Riou: Calculation of medium-frequency vibrations over a wide frequency range. Comput. Methods Appl. Mech. Eng. 194 (2005), 3167–3191. MR 2142539

[24] I.  Babuška, F.  Ihlenburg, T.  Strouboulis, and S. K.  Gangaraj: A posteriori error estimation for finite element solutions of Helmholtz’ equation. Part  I: The quality of local indicators and estimators. Int. J.  Numer. Methods Eng. 40 (1997), 3443–3462. MR 1471617

[25] I.  Babuška, F.  Ihlenburg, T.  Strouboulis, and S. K.  Gangaraj: A posteriori error estimation for finite element solutions of Helmholtz’ equation. Part  II: Estimation of the pollution error. Int. J.  Numer. Methods Eng. 40 (1997), 3883–3900. MR 1475346

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[27] I.  Babuška, S.  Sauter: Is the pollution effect of the FEM avoidable for the Helmholtz equation considering high wave numbers?, SIAM J.  Numer. Anal. 34 (1997), 2392–2423. MR 1480387

[28] T.  Strouboulis, I.  Babuška, and R.  Hidajat: The generalized finite element method for Helmholtz equation: theory, computation, and open problems. Comput. Methods Appl. Mech. Eng., Accepted for publication. MR 2240576

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[32] T.  Strouboulis, L.  Zhang, D.  Wang, and I.  Babuška: A posteriori error estimation for generalized finite element methods. Comput. Methods Appl. Mech. Eng. 195 (2006), 852–879. MR 2195292