Paid iPad app: http://itunes.apple.com/us/app/britannica-kids-us-presidents/id477792298?mt=8&uo=4&at=10l6SU
Paid iPhone app: http://itunes.apple.com/us/app/britannica-kids-us-presidents/id477792298?mt=8&uo=4&at=10l6SU
Website: http://www.nps.gov/elis/forteachers/curriculummaterials.htm
Free iPad app: https://itunes.apple.com/US/app/id550965686?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/US/app/id550965686?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/presidents-vs.-aliens-lite/id427421823?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/presidents-vs.-aliens/id427418941?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/presidents-vs.-aliens-lite/id427421823?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/presidents-vs.-aliens/id427418941?mt=8&uo=4&at=10l6SU