1. Actualit\'{e}s Scientifiques et Industrielles [Current Scientific and Industrial Topics], No. 1293;Bourbaki, N.,1961
2. Maximal fields with valuations;Kaplansky, Irving;Duke Math. J.,1942
3. Modules over Dedekind rings and valuation rings;Kaplansky, Irving;Trans. Amer. Math. Soc.,1952
4. W. Krull, Allgemeine Bewertungstheorie, J. Reine Angew. Math. 167 (1932), 160-196.