from the link:

"...diagram has been uncovered which shows that Iranian scientists are calculating the "nuclear explosive yield" of a major nuclear weapon. ..

...Diagrams of Iran's work were passed to the International Atomic Energy Agency ..."

Lots of vagueness about the origin of the document, and the channels through which it was passed.

Nowhere does it say 'Iran did this or that', just that a document to that effect has surfaced.