Sellers, Charles
Rand Mcnally Publishing, 1974
Buku Teks
edited by Annette ten Teije
Springer-Verlag, 2012
eBooks
Nagelkerke, Gerard A.
Leiden Library of the Royal Institute of Linguistics and Anthropology 1982
Buku Referensi
Heawood, Edward, 1863-1949, author
Paper Publications Society, 1986
Buku Teks
edited by Michela Milano
Springer-Verlag, 2012
eBooks