Wilber, Charles K.
McGraw-Hill , 1992
Buku Teks
North-Holland, 1972
Buku Teks
Angelopoulos, Angelos
Preager, 1972
Buku Teks
Hettne, Bjorn, 1939-, author
Pustaka Sinar Harapan, 1982
Buku Teks
Thirlwall, Anthony Philip, author
English Language Book Society, 1978
Buku Teks