1. Abdelatif, T.E.: 1988,Astrophys. J. 333, 395
2. Abdussamatov, H.I., Krat, V.A.: 1969,Solar Phys. 9, 420
3. Acton, D.S.: 1989, inHigh Spatial Resolution Solar Observations, O. von der Lühe (Ed.), National Solar Obs., Sunspot, NM, p. 71
4. Acton, D.S.: 1990, Ph.D. Thesis
5. Akima, H.: 1970JACM 17, 589