1. Zur theorie der charactere der abelschen topologischen gruppen;Gelfand;Mat Sb,1941
2. Commutative Normed Rings;Gelfand,1964
3. Functional Analysis and Semi-Groups;Hille,1957
4. Banach Algebras;Larsen,1973
5. An Introduction to the Local Spectral Theory;Laursen,2000