1. Basu, S., Antia, H.M.: 2003, Astrophys. J. 585, 553.
2. Beckers, J.M.: 1978. In: Belvedere, G., Paternò, L. (eds.) Proceedings Workshop on Solar Rotation, University of Catania, Catania, p. 166.
3. Beckers, J.M.: 2005, Bull. Am. Astron. Soc. 37, 464.
4. Beckers, J.M., Taylor, W.R.: 1980, Solar Phys. 68, 41.
5. González Hernández, I., Komm, R., Hill, F., Howe, R., Corbard, T., Haber, D.A.: 2006, Astrophys. J. 638, 576.