Briggs, Lawrence Palmer
The American Philosophical Society, 1951
Buku Teks
CRC press, 2020
eBooks
Hunt, Elgin F., author
MacMillan, 1987
Buku Teks
Sumner, William Graham
New Haven Yale University Press, 1950
Buku Teks
Bierstedt, Robert, author
McGraw-Hill, 1964
Buku Teks