1. Allasia, G. (1995): A class of interpolating positive linear operators: Theoretical and Computational aspects. In: Singh, S.P., Carbone, A. and Watson, B. (eds.): Approximation theory, Wavelets and Applications. ( Kluwer Academy Publishers, Dordrecht/Boston/London ).
2. Achim, A., Richer, F. and Saint-Hilaire, J. (1991): Methodological considerations for the evaluation of spatio-temporal source models. Electroenceph. clin. Neurophysiol., 1991, 79: 227 – 240.
3. Backus, G.E. and Gilbert, J.F. (1967): Numerical applications of a formalism for geophysical inverse problems. Geophys. J. Roy. Astron. Soc. 13: 247 – 276.
4. Backus, G.E. and Gilbert, J.F. (1968): The resolving power of gross earth data. Geophys. J. Roy. Astron. Soc. 16: 169 – 205.
5. Backus, G.E. and Gilbert, J.F. (1970): Uniqueness in the inversion of gross earth data. Phil. Trans. R. Soc. 266: 123 – 192.