Transaction Processing Concepts and Techniques,
by Jim Gray and Andreas Reuter, Morgan Kaufmann Publishers. We recommend chapters 1, 4 (skip 4.6, 4.7, 4.9, 4.10 and 4.11), 7, 9, 10.3, and 10.4.

An Introduction to Database Systems, Volume 1,
by C.J. Date, Addison Wesley Longman Publishers. In the 5th Edition, we recommend chapters 1, 2, 3, 16 and 17.

Concurrency Control and Recovery in Database Systems,
by Berstein, Goodman, Hadzilaco.

Technical Papers Relating to the Berkeley DB Structure:

LIBTP: Portable Modular Transactions for UNIX,
Margo Seltzer and Michael Olson, USENIX Conference Proceedings, Winter 1992.

Operating System Support for Database Management,
Michael Stonebraker, Communications of the ACM 24(7), 1981, pp. 412-418.

Technical Papers Relating to the Hash Access Method:

A New Hashing Package for UNIX,
Margo Seltzer and Oz Yigit, USENIX Conference Proceedings, Winter 1991.

Dynamic Hash Tables,
Per-Ake Larson, Communications of the ACM, April 1988.

Linear Hashing: A New Tool for File and Table Addressing,
Witold Litwin, Proceedings of the 6th International Conference on Very Large Databases (VLDB), 1980

Technical Papers Relating to the Btree Access Method:

The Ubiquitous B-tree,
Douglas Comer, ACM Comput. Surv. 11, 2 (June 1979), pp. 121-138.

Prefix B-trees,
Bayer and Unterauer, ACM Transactions on Database Systems, Vol. 2, 1 (March 1977), pp. 11-26.

The Art of Computer Programming Vol. 3: Sorting and Searching,
D.E. Knuth, 1968, pp. 471-480.

Technical Papers Relating to the Recno Access Method:

Document Processing in a Relational Database System,
Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman, Nadene Lynn, Memorandum No. UCB/ERL M82/32, May 1982.