@article{Mascotto-Pichler:2020,
author = {Mascotto, L. and Pichler, A.},
title = {Extension of the nonconforming {T}refftz virtual element method to the {H}elmholtz problem with piecewise constant wave number},
journal={Appl. Numer. Math.},
year={2020},
volume={155},
pages={160--180},
publisher={Elsevier}
}