Leedy, Paul D. Practical research : planning and design / Paul D. Leedy, Jeanne Ellis Ormrod. - 9th ed. - Upper Saddle River, NJ : Merrill, c2010 - xvii, 336 p. : 28 cm. Original: E-C7/00333 ISBN: 0131365665 9780131365667 Subjects--Topical Terms: Research Subjects--Index Terms: Phương pháp nghiên cứu Tri thức Dewey Class. No.: 001.4