A subringof containing the ring of integral elements of the field , distinct from , and not contained in any other subring of distinct from , is called a maximal ring of the algebra . In a division algebra, the only maximal ring is the ring of integral elements.
1970 [Frederick Ungar Publishing], John R. Schulenberger (translator), B. L. van der Waerden, Algebra, Volume 2, 1991, Springer, 2003 Softcover Reprint, page 172,
If is the ring of integral elements in a commutative ring (over a subring ) and if the element of is integral over , then is also integral over (that is, contained in ).
2004, Michiel Hazewinkel, Nadiya Gubareni, V. V. Kirichenko, Algebras, Rings and Modules, Volume 1, Kluwer Academic Publishers, page 209,