Haupt, Arthur
Population Reference Bureau, 1998
Buku Referensi
International Labour Office
International Labour Office, 1961
Buku Teks
UNESCO, 1977
Buku Teks
Hertzler, Joyce O.
University of Nebraska Press , 1956
Buku Teks
Hertzler, Joyce O.
University of Nebraska Press , 1956
Buku Teks