1. Morten Willatzen, Lok C. Lew Yan Voon, Appala Naidu Gandi, and Udo Schwingenschl？gl,
"3D Continuum Phonon Model for Group-IV 2D Materials", Beilstein Journal of Nanotechnology
8, 1345-1356 (2017). (doi:10.3762/bjnano.8.136).
2. J. Christensen, M. Willatzen, V. R. Velasco, and M.-H. Lu, "Parity-time synthetic phononic
media," Phys. Rev. Lett. 116, 207601 (2016).
3. M. Willatzen and Z. L. Wang, "Uni?ed treatment of coupled optical and acoustic phonons in
piezoelectric cubic materials," Phys. Rev. B 92, 224101 (2015).
4. L. C. Lew Yan Voon, A. Lopez-Bezanilla, J. Wang, Y. Zhang, and M. Willatzen, "Effective
Hamiltonians for phosphorene and silicene," New J. Phys. (ISSN: 1367-2630) (DOI:
http://dx.doi.org/10.1088/1367-2630/17/2/025004) 17 (2015).
5. M. Willatzen and J. Christensen, "Acoustic gain in piezoelectric semiconductors at epsilon-near-zero
response," Phys. Rev. B Rapid Com. 89, 041201(R) (2014).

6. J. Christensen, V. Romero-Garcia, R. Pico, A. Cebrecos, F. J. Garcia de Abajo, N. A.
Mortensen, M. Willatzen, and V. J. Sanchez-Morcillo, "Extraordinary absorption of sound
in porous lamella-crystals," Scienti?c Reports 4, 4674 (2014).
7. M. Willatzen, A. Pors, and J. Gravesen, "Strong curvature effects in Neumann wave problems,"
J. Math. Phys. 53 (8), 083507(15) (2012).
8. L. C. Lew Yan Voon and M. Willatzen, "The k.p Method - Electronic Properties of Semiconductors,"
Springer, Berlin (ISBN 978-3-540-92871-3), 445 pages, August 2009.
9. M. Willatzen and L.C. Lew Yan Voon, "Separable Boundary-Value Problems in Physics,"
Wiley, Weinheim (ISBN 978-3-527-41020-0), 398 pages, April 2011.