https://ctools.umich.edu/dav/715d3da9-f664-4281-80f6-e60869a420c8
http://docs.python.org/lib/module-threading.html
http://www.devshed.com/c/a/Python/Basic-Threading-in-Python/3/
http://docs.python.org/lib/timer-objects.html
http://heather.cs.ucdavis.edu/~matloff/Python/PyThreads.pdf
http://artfulcode.nfshost.com/files/multi-threading-in-python.html
http://artfulcode.nfshost.com/files/multi-threading-in-python.html
Locking:
http://linuxgazette.net/107/pai.html