1. Alfvén, H.: 1950,Cosmical Electrodynamics, Oxford University Press, Oxford.
2. Ananthakrishnan, R. and Madhaven, Nagar: 1954,Kodaikanal Obs. Bull., No. 137, 7.
3. Babcock, H. D.: 1961,Astrophys. J. 133, 572.
4. Bocchino, G.: 1933,Mem. Obs. Arcetri. 51, 7.
5. Bocchino, G.: 1935,Mem. Obs. Arcetri. 67, 7.