Description of transaction model for indexes

Hello!

The transaction model is discussed in several areas:
http://www.packtpub.com/article/transaction-model-of-postgresql
The POSTGRES Data Model (1987)
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.48.8578
The Design of POSTGRES (1986)
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.48.1422

However: Is there a paper available, how indexes are handled inside the
transaction (e.g. visibility (not handled), concurrency, etc.)?
E.g. What happens on SELECT/INSERT/UPDATE/DELETE?

Some aspects can be found in:
http://www.pgcon.org/2008/schedule/attachments/54_PGCon2008-HOT.ppt

Thnx.

Ciao,
Gerhard

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