Gaya APA
Leedy, P, D. (1980).
Practical Research Planning and Design (Thrid Edition).
United States of America:
Macmillan Publ.Co..
Gaya MLA
Leedy, Paul, D..
"Practical Research Planning and Design".
Thrid Edition
United States of America:
Macmillan Publ.Co.,
1980.
Textbook.