Breaking the ideological barrier
 Artikel Jurnal
Gilbert, Doris W.
Breaking the reading barrier
Prentice-Hall, 1991
 Buku Teks SO
Tokos, Sherry
Breaking the age barrier
Viking Canada, 2003
 Buku Teks SO
McGregor, Craig
The Great Barrier Reef
Time-Life Books, 1974
 Buku Teks SO
Maryam Ahmad Assegaf
Desain kebun binatang = Zoo barrier design
Fakultas Teknik Universitas Indonesia, 2014
 UI - Skripsi Membership