George E. Walker ... [and others]
Jossey-Bass, 2008
Buku Teks
Suprapto
Kementerian Agama, 2019
Artikel Jurnal
Voice of America Forum Lectures , 1968
Buku Teks
Bryson, George D.
McGraw-Hill , 1964
Buku Teks
Kirby, David K.
Gale Research, 1975
Buku Referensi