1. G. Alessandrini, “Stable Determination of Conductivity by Boundary Measurements”, Applicable Analysis, Vol. 27, (1988), pp. 153–172.
2. G. Alessandrini and J. Sylvester, “Stability for a Multidimensional Inverse Spectral Theorem”, Comm. Math. Phys., Vol. 5, No. 5, (1990), pp. 711–736.
3. M.I. Belishev, “On an approach to Multidimensional Inverse Problems for the wave equation”, Dokl. Akad. Nauk SSSR (in Russian), Vol. 297, No. 3, (1987), pp. 524–527.
4. M.I. Belishev, “Boundary control in reconstruction of manifolds and metrics (the BC method),” Inverse Problems, Vol. 13 (1997), No. 5 pp. R1–R45.
5. G. Borg, Eine Umkehrung der Sturm-Liouvilleschen Eigenwertaufgabe, Acta Math. Vol. 78, (1946), pp. 1–96.