1. Antonucci, E., Hoeksema, J. T., and Scherrer, P. H.: 1990,Astrophys J. 360, 296.
2. Arakawa, A.: 1966,J. Comput. Phys. 1, 119.
3. Bumba, V. and Howard, R.: 1969,Solar Phys. 7, 28.
4. Bumba, V.: 1987,Solar Phys. 110, 51.
5. DeLuca, E. E. and Gilman, P. A.: 1991, in A. N. Cox, W. C. Livingston, and M. S. Matthews (eds.),Solar Interior and Atmosphere, The University of Arizona Press, Tucson, p. 275.