Wheeler, Jesse H.
Henry Holt , 1960
Buku Teks
Israel, Saul, author
Holt, Rinehart and Winston, 1980
Buku Teks
McNally, Rand, author
Rand McNally & Co, 1957
Buku Referensi
Minshull, Roger
Hutchinson University Library, 1971
Buku Teks
Bradshaw, Michael J, author
McGraw-Hill, 2012
Buku Teks