Research Report 2005 : school of electrical & electronic engineering
Singapura : Nanyang Technological University, 2005,
Majalah, Jurnal, Buletin
Annual Report 1999/World Bank
Washington, D.C. World Bank 1999,
Buku Teks
CIRAD 2003
London : CIRAD, 2003,
Buku Teks
Laporan tengah tahunan Universitas Sumatera Utara 1992
Universitas Sumatera Utara, 1992
Buku Referensi
Laporan tahunan Bank Indonesia 1995/1996/Bank Indonesia
Jakarta Bank Indonesia 1996,
Buku Teks