1. W. A. Adkins, and S. H. Weintraub, Algebra, an Approach via Module Theory (Springer, New York, 1992).
2. E. Artin, Galois Theory (University of Notre Dame Press, South Bend, Ind.-London, 1959).
3. Topology of the quasi-ordinary singularities;Gau;Topology,1986
4. J. Lipman, Quasi-ordinary Singularities of Embedded Surfaces, Ph. D. thesis, Harvard University (1965), in: Collected Papers of Joseph Lipman, Queen's Papers in Pure and Applied Mathematics Vol. 117 (Queen's University, Kingston (Ontario), 2000).
5. M. Micus, Zur formalen Äquivalenz von quasigewöhnlichen Singularitäten, Ph. D. thesis, University of Paderbron (1987).