Manger, Jason J.
The essential internet information guide
McGraw-Hill, 1995
Buku Referensi
Schwedt, Georg
The essential guide to environmental chemistry
John Wiley & Sons, 2001
Buku Referensi
Warbuton, Nigel
Philosophy: the essential study guide
Routledge, 2004
Buku Teks SO
Schwedt, Georg
The Essential Guide to environmental chemistry
John Wiley & Sons, 2001
Buku Teks SO
Griffith, H. Winter
Healing Herbs: The Essential Guide
Fisher Books, 2000
Buku Teks SO