1. Hadamard, J. (1923) Lectures on the Cauchy problem in linear partial differential equations. Yale University Press, New Haven, USA.
2. Santamarina, J. C. and Fratta, D. (2005) Discrete signals and inverse problems. An Introduction for Engineers and Scientists. p. 276, John Wiley & Sons Ltd., Chichester, England.
3. Lawson, C. L. and Hanson, R. J. (1974) Solving linear least squares problems. Prentice-Hall, Englewood Cliffs, New Jersey.
4. Hansen, P. C. (1998) Rank-deficient and discrete ill-posed problems: numerical aspects of linear inversion, in Monographs on Mathematical Modeling and Computation, vol. 4, Society for Industrial and Applied Mathematics Philadelphia PA.
5. Tikhonov, A. N. and Arsenin, V. Y. (1977) Solutions of Ill-Posed Problems. John Wiley & Sons, New York.