Well, we could start with Iran’s own admissions.
http://www.newsmax.com/Headline/iran-nuclear-weapons-israel/2010/10/05/id/372644
http://www.haaretz.com/news/international/report-ex-iran-diplomat-admits-working-toward-nuclear-bomb-with-north-korea-s-help-1.332312
http://www.thedailypoint.com/world-news/ex-iran-diplomat-admits-working-toward-nuclear-bomb-with-north-koreas-help-1319.html
You also have that North Korea has been caught supplying weapon information to Iran. http://fpc.state.gov/documents/organization/124931.pdf
I can keep going and going but that is all I have time for this morning.
Are .com references the same as the evidence Paul is talking about? How have the other candidates responded when asked about this?