Charles, C. M. Introduction to educational research / C.M. Charles, Craig A. Mertler. - 4th ed. - Boston : Allyn and Bacon, 2002. - xxiii, 392 p. : ill ; 25 cm. ISBN: 0321081757 (alk. paper) LCCN: 2001022425 Subjects--Topical Terms: Education--Research. Dewey Class. No.: 370/.7/2