American Public Transit Association. [http://aptastandards.com/Documents/PublishedStandards/Farecard/tabid/331/language/en-US/Default.aspx "Manual of Standards and Practices for Universal Transit Farecards."] 2006-2009.
: This link leads to
separate downloads of five chapters of standards for use of contactless fare cards , which were developed between 2006 and 2009 by the American Public Transit Association's Standards program. These standards include an overview of contactless cards in general, as well as more technical chapters on the security and maintenance of systems that use them.