@article{Cha-Des-Cia-2017,
    author={Stéphanie Chaillat and Luca Desiderio and Patrick Ciarlet },
    title={Theory and implementation of H-matrix based iterative and 
           direct solvers for Helmholtz and elastodynamic oscillatory 
           kernels },
    doi={10.1016/j.jcp.2017.09.013 },
    journal={Journal of Computational Physics },
    year={2017 },
    month={12},
    volume={351 },
    pages={165–186},
}