By Kopperman Ralph D.   Tkachuk Vladimir V.   in Quaestiones Mathematicae

ISSN:1727-933X|26|3|354-369

Taylor & Francis Ltd‎(2003)‎

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By Bukatin Michael   Kopperman Ralph   Matthews Steve   Pajoohesh Homeira   in American Mathematical Monthly

ISSN:1930-0972|116|8|708-718

Mathematical Association of America‎(2009)‎

Access to resources Favorite 10.119601