Determining the Oracle Client and Server Versions

>sqlplus scott/tiger@testOrcl
SQL*Plus: Release 10.2.0.3.0 - Production on Mon Mar 21 04:33:33 2009 <-- Client Version
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Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production <-- Server Version
With the Partitioning, OLAP and Data Mining options