1. Abetti, G.: 1929, Handbuch Astrophys. 4.
2. Report No. 42;F. Albregtsen,1974
3. Andersen, T., Dunn, R., and Engvold, O.: 1984, ?LEST Design Study?, LEST Foundation Technical Report No. 7, September 1984.
4. Artus, H.: 1976, Jena Rev. 3, 138.
5. Baker, J.: 1954, Astron. J. 59, 74.