Oracle security handbook - Aaron Newman and Marlene Theriault - published by Oracle Press.
Oracle in a nutshell - A desktop Quick reference - Rick Greenwald and David C Kreines - Published by O'Reilly
Expert one-on-one - Thomas Kyte - Published by Wrox Press
Internet security with Oracle Row-Level security - Roby Sherman - http://www.interealm.com/roby/technotes/8i-rls.html
Oracle documentation - http://tahiti.oracle.com
Oracle 8i Virtual Private Databases - Tim Gorman - http://www.evdbt.com/VPD.pps
Practical Oracle 8i - Building efficient databases - Jonathan Lewis - Published by Addison Wesley