1. De Jager, C. and Neven, L.: 1967a, Solar Phys. 1, 27.
2. De Jager, C. and Neven, L.: 1967b, Bull. Astron. Inst. Neth. Suppl. series 1 (8), 325 = Comm. Obs. Roy. Belg. series A2.
3. Gingerich, O. and De Jager, C.: 1968, Solar Phys. 3, 5.
4. Heintze, J. R. W., Hubenet, H. and De Jager, C.: 1964, Bull. Astron. Inst. Neth. 17, 442.
5. Kirshna Swamy, K. S.: 1968, J. Quant. Spectrosc. Radiat. Transfer 8, 855.