There's an article in the June 26th issue of Visa Business News. You should be able to access it through Visa Online.
In summary, effective October 17th 2014 Visa is extending Zero Liability coverage to U.S.ATM transactions conducted over the VIsa and Plus networks.
Visa is not requiring issuers to notify cardholders of the change.
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Let's start at the very beginning; A very good place to start...