Grolier, 1967
Buku Referensi
Cornell University, 1956
Buku Referensi
Becker, Beverley C.
[American Library association, ], 2002
eBooks
Lesesne, Teri S.
[American Library association, ], 2002
eBooks
compiled by Hugh Borton [and others] rev, and enlarged, comp. by William W. Lockwood
Harvard University Press, 1954
Buku Teks SO