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Open Mathematics > 2011 > 9 > 6 > 1380-1388
Discussiones Mathematicae - General Algebra and Applications > 2003 > 23 > 2 > 115-123
Open Mathematics > 2011 > 9 > 6 > 1380-1388
Discussiones Mathematicae - General Algebra and Applications > 2003 > 23 > 2 > 115-123