1. Ardeberg A. and Virdefors B., 1972, Astron. And Astrophys. 20, 177.
2. Bell R.A., 1973, Monthly Not. R.A.S., 164, 197.
3. Bell R.A., And Gustafsson B., 1975, In Proceedings Of “Multicolour Photometry And The Theoretical Hr Diagram” (Eds. Philip Andhayes), Dudley Obs. Report, 9, P. 319.
4. Clausen J.V., 1973, Iau Symposium 50 (Eds. Fehrenbach And Westerlund), P. 134.
5. De Jager C., And Nieuwenhuijzen H., 1975, Proceedings Of Conference On Image Processing In Astronomy, Reidel, Dordrecht.