1. E. Becker, The real holomorphy ring and sums of 2n-th powers, in: Géométrie Algébrique Réelle et Formes Quadratiques, edited by J.-L. Colliot-Thélène et al., Lecture Notes in Mathematics Vol. 959 (Springer, Berlin, 1982), pp. 139-181.
2. Sums of powers in rings and the real holomorphy ring;Becker;J. Reine Angew. Math.,1996
3. G. W. Brumfiel, Partially Ordered Rings and Semi-Algebraic Geometry, London Mathematical Society Lecture Note Series Vol. 37 (Camb. Univ. Press, Cambridge, 1979).
4. Normal spectral spaces and their dimensions;Carral;J. Pure Applied Algebra,1983
5. L. Gillman, and M. Jerison, Rings of Continuous Functions, Graduate Texts in Mathematics Vol. 43 (Springer, Berlin, 1976).