@article{Kov-Lad-Rio-Bon-2012,
    author={Louis Kovalevsky and Pierre Ladevèze and Hervé Riou and Marc 
           Bonnet },
    title={The Variational Theory of Complex Rays for three-dimensional 
           Helmholtz problems },
    doi={10.1142/S0218396X1250021X },
    journal={Journal of Computational Acoustics },
    year={2012 },
    volume={20 },
    pages={1250021},
}