1. S.J. Bhatt, spectrally convex Banach algebras, Indian J. Pure. Appl. Math. 10 (1976) 720–730.
2. Linear topological division algebras
3. H. Cartan, Theorie des filtres, CR Acad Paris, 205, (1937) 595–598.
4. N. Bourbaki, General Topology. Sci. Ltd, 858. Paris. 938, (1940).
5. G. Choquet, Convergences. Ann. Univ. Grenoble. Sect. Sci. Math. Phys. (N.S.), 23:57–112, (1948).