1. Beckers, J. M.: 1987, in L. B. Robinson (ed.),Instrumentation for Ground-Based Optical Astronomy, Springer-Verlag, Berlin, p. 315.
2. Beckers, J. M.: 1988a, VLT-IPF R&D Note 88-2.
3. Beckers, J. M.: 1988b, in D. M. Alloin and J.-M. Mariotti (eds.),Diffraction Limited Imaging with Very Large Telescopes, Kluwer Academic Publishers, Dordrecht, Holland, p. 365.
4. Beckers, J. M. 1989a, VLT-IPF R&D Note 89-5.
5. Beckers, J. M.: 1989b, VLT-IPF R&D Note 89-6.