Works citing   [Math. Res. Lett. 14 (2007), 107-111]

1. J. B. Kennedy:
   The nodal line of the second eigenfunction of the Robin Laplacian in R^2 can be closed,
   J. Differential Equations 251 (2011), 3606-3624.
   
   
2. P. Amore, M. Rodriguez, C. A. Terrero-Escalante:
   Bound states in open-coupled asymmetrical waveguides and quantum wires,
   J. Math. Phys.: Math. Theor. 45 (2012), 105303.
   
   
3. J. B. Kennedy:
   Closed Nodal Surfaces for Simply Connected Domains in Higher Dimensions,
   Indiana Univ. Math. J. 62 (2013), 785-798.
   
   
4. D.-H. Yang, B.-Z. Guo:
   On nodal line of the second eigenfunction of the Laplacian over concave domains in R^2,
   J. Syst. Sci. Complex. 26 (2013), 483-488.