What's New in Python 2.5 - PEP 342: New Generator Features
http://docs.python.org/release/2.5/whatsnew/pep-342.html

PEP 342 -- Coroutines via Enhanced Generators
http://www.python.org/dev/peps/pep-0342/

PEP 380 -- Syntax for Delegating to a Subgenerator
http://www.python.org/dev/peps/pep-0380/

Coroutines For the Working Python Developer
http://sdiehl.github.io/coroutine-tutorial/