Henry Holt and Co., 1934
Buku Teks
Lyon, Leverett S., author
The Brookings Institution, 1940
Buku Teks
Koontz, Harold, author
McGraw-Hill, 1956
Buku Teks
Redford, Emmette S., author
Macmillan, 1952
Buku Teks
Steiner, George A. (George Albert), 1912-, author
McGraw-Hill, 1953
Buku Teks