\bibitem{Lapidus91}     M.L.Lapidus   \hskip 2mm
                        {\it Fractal Drum, Inverse Spectral Problems for Elliptic Operators and a Partial
                        Resolution of the Weyl-Berry Conjecture},
                        Trans.Amer.Math.Soc. {\bf 325} (2), 465-529, 1991.