The Hague, 1972
Buku Teks SO
edited by Ulrich Ammon, Norbert Dittmar, Klaus J. Mattheier
Walter de Gruyter, 1987
Buku Referensi
edited by Ulrich Ammon, Norbert Dittmar, Klaus J. Mattheier
Walter de Gruyter, 1988
Buku Referensi
Bram, Joseph
Random House, 1955
Buku Teks SO
Malmstrom, Jean
Hayden Book Company, 1965
Buku Teks SO