Discussiones Mathematicae - General Algebra and Applications
Discussiones Mathematicae - General Algebra and Applications > 2004 > 24 > 1 > 31-42
Discussiones Mathematicae - General Algebra and Applications > 2008 > 28 > 2 > 251-259
Discussiones Mathematicae - General Algebra and Applications > 2008 > 28 > 2 > 139-145
Discussiones Mathematicae - General Algebra and Applications > 2010 > 30 > 2 > 207-215