Langer, Maria
Quicken 2000 : the official guide
Osborne/McGraw-Hill, 1999
 Buku Referensi
Guide to official statistics
Central Statistical Office
Her Majesty`s Stationery Office, 1986
 Buku Referensi
Stein, Lincoln D.
Official guide to programming with CGI.pm
Wiley, 1998
 Buku Teks SO
Volitich, Dan; Oehler, Karsten
IBM Cognos TM1 : the official guide
McGraw-Hill, 2012
 Buku Teks SO
Hayes, Denis
The Official earth day guide to planet repair
Island Press, 2000
 Buku Teks