1. The real holomorphy ring and sums of 2nth powers;Becker,1982
2. On real holomorphy rings;Berr,1995
3. Commutative Algebra, Chapters 1–7;Bourbaki,1985
4. General Topology, Chapters 1–4;Bourbaki,1998
5. Valuations of function fields from the geometrical point of view;Brocker;J. Reine Angew. Math.,1986