Sergey Leble, author
TASK, 2017
Artikel Jurnal
Rogowski, Krzysztof, author
Task, 2018
Artikel Jurnal
edited by Michael B. Gregg
Oxford University Press, 2002
Buku Teks
Seelye, Elwyn E.
New York: John Wiley & Sons, 1954
Buku Teks
Barrett, William E., author
Popular Library, 1962
Koleksi Publik