1. Abdussamatov, H. I. and Stoyanova M. N.: 1971, Soln. Dann., No. 10, 72.
2. Beckers, J. M.: 1964 ?A Study of the Fine Structure of the Solar Chromosphere?, Sacramento Peak Obs. Contr., No. 75.
3. Heintze, J. R. W.: 1969, Bull. Astron. Inst. Neth. 20, 137.
4. Karpinsky, V. N.: 1965, Izv. Pulkovo 178, 84.
5. Krat, V. A.: 1962, Izv. Pulkovo 170, 2.