Hearing the shape of a compact Riemannian manifold with a finite number of piecewise impedance boundary conditions. Zayed, E.M.E. (1997) International Journal of Mathematics and Mathematical Sciences
Hearing the shape of a general convex domain: an extension to higher dimensions Zayed, E.M.E. (1991) Portugaliae mathematica
Hearing the shape of membranes: Further results. Zayed, E.M.E. (1990) International Journal of Mathematics and Mathematical Sciences