Looking for in-depth books on Oracle

I am looking for books on Oracle. I remember seeing similar requests flying by, but I never bothered looking up the answers.

I am more interested in internals and architecture aspects than in 'how to use' aspects.

/albert

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Albert Godfrind                            
Digital Equipment Corporation      INET:  godfrind_at_beagle.enet.dec.com
European Technical Center                 Albert.Godfrind_at_vbo.mts.dec.com
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