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\bibitem{Caratelli_etal2013} {\textquotedblleft}\textit{Spherical harmonic solution of the Robin problem for the Helmholtz equation in a supershaped shell}{\textquotedblright}. Caratelli D, Gielis J, Tavkhelidze I, Ricci PE, Applied mathematics \textbf{4}, 263 (2013).   http://doi.org/10.4236/AM.2013.41A040

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