Chajda, Ivan. <br/><br/>
Directoids:  an algebraic approach to ordered sets/ 
Ivan Chajda, Helmut Langer. 
 - Lemgo, Germany:  Heldermann Verlag,  2011. 
 - 176 pages:  illustrations;  24 cm. 
 - Research and exposition in mathematics;  32 .
 - Research and exposition in mathematics;  32. .
<br/><br/>Includes bibliographical references and index. 
<br/><br/><label>ISBN: </label>9783885382324 3885382326 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Ordered sets
<br/><br/><label>Dewey Class. No.: </label>511.332