1. Bifurcus semigroups and rings;Adams;Involve,2009
2. Number theory of matrix semigroups;Baeth;Linear Algebra Appl.,2011
3. N. Baeth, D. Smertnig, Factorization theory in noncommutative settings, preprint.
4. Free Rings and Their Relations;Cohn,1985
5. On Quaternions and Octonions: Their Geometry, Arithmetic, and Symmetry;Conway,2003