Abell, George O. <br/><br/>Exploration of the universe/ George O. Abell.--  -- Sixth edition.  -- Philadelphia:  Saunders College Publishing,  1991. <br/>vii.,  col.: ill.;  28. <br/><br/> Includes index. <br/><br/><label>ISBN: </label>0030946662 <br/><br/><label>Subjects--Topical Terms: </label><br/>Astronomy<br/><br/><label>Dewey Class. No.: </label>HS Cir 520 A34 1991