1. G. R. Lemaitre: Astronomical Optics and Elasticity Theory — Active Optics Methods (Springer, Heidelberg, 2012) 3rd ed.
2. E. E. Everhart: Appl. Opt. 5 (1966) 712.
3. G. R. Lemaître: Appl. Opt. 11 (1972) 1630.
4. G. R. Lemaitre and C. R. Acad: Sci. Paris, Ser. B 282 (1976) 87.
5. M. Ferrari: Astron. Astrophys. 274 (1994) 12.