The physicist Freeman Dyson, who knew Serber, Oppenheimer, and other participants of the Manhattan Project, called the Primer a "legendary document in the literature of nuclear weapons". He praised "Serber's clear thinking", but harshly criticized the Primer ' s publication, writing "I still wish that it had been allowed to languish in obscurity for another century or two." Acknowledging that it was unclassified in 1965, and that it can't be useful to any bomb designer from 1950, Dyson still thinks that such publication can be dangerous: