Annoying reminder to upgrade from 13.04 to 13.10

I am currently running Lubuntu 13.04

Every time that some updates are installed, the system pops a window offering to upgrade to 13.10
(This is getting almost as bad as Windows)

I tried 13.10, and prefer 13.04.

How do I stop the pop-ups from ding-donging me to upgrade to 13.10 ?

Thanks.