Object-Oriented Modeling and Design. James Rumbaugh, Michael Blaha, William Premerlani, Frederick Eddy, and William Lorensen. Prentice-Hall, 1991.
An excellent treatment of implementing OO models in relational databases.
Object Persistence. Roger Sessions. Prentice Hall, 1996.
A discussion of the CORBA Persistence architecture. Interesting as much for the discussion of politics behind such committees, as the technical material.
CORBA Persistence Service Specification, Object Management Group (OMG), at http://www.omg.org.
PJava: Orthogonal Persistence for Java, at http://www.dcs.gla.ac.uk/pjava/. Look especially for the design paper entitled "Design Issues for Persistent Java: a Type-Safe, Object-Oriented, Orthogonally Persistent System."
Object Database Management Group (ODMG): http://www.odmg.org.
Taming C++: Pattern Classes and Persistence for Large Projects. Jiri Soukup. Addison-Wesley, 1994.
"Equal Rights for Functional Objects, or, The More Things Change, The More They Are the Same." Henry Baker.
This paper shows you that there's much more to object identity than meets the eye. Download from ftp://ftp.netcom.com/pub/hb/hbaker/ObjectIdentity.html.