Longman Community Information
Longman Grup, 1994
Buku Referensi
School Government Publishing Co., [date of publication not identified]
Buku Referensi
edited and compiled by Wolodymyr Maksymiw
Longman, 1990
Buku Referensi
J. Whitaker & Sons, 1995
Buku Referensi
edited by Ellen M. Codlin
Aslib, 1986
Buku Referensi