Éléments tertiaires d'une (T)-algèbre
Erratum to "On rings with a unique proper essential right ideal" (Fund. Math. 183 (2004), 229-244)
Essential Cover and Closure
2000 Mathematics Subject Classification: 16N80, 16S70, 16D25, 13G05.We construct some new examples showing that Heyman and Roos construction of the essential closure in the class of associative rings can terminate at any finite or the first infinite ordinal.