1. Asplund, E.: Fréchet differentiability of convex functions. Acta Math. 121, 31–47 (1968)
2. Beauzamy, B.: Introduction to Banach Spaces and Their Geometry, 2nd revised edn. North-Holland, Amsterdam (1985)
3. Benvenuto, F., Zanella, R., Zanni, L., Bertero, M.: Nonnegative least-squares image deblurring: improved gradient projection approaches. Inverse Probl. 26, 025004 (2010) (18 pp.)
4. Bertero, M., Boccacci, P.: Introduction to Inverse Problems in Imaging. Institute of Physics Publ., Bristol (1998)
5. Bertsekas, D.P.: Nonlinear Programming. Athena Scientific, Belmont (1995)