Text: They contend that the so-called Venona intercepts, a few of which have been released, show definitively not only that Alger Hiss and the Rosenbergs were spies but also that there was far more Soviet string-pulling behind American Communism than anyone ever knew.
Entailment: They assert that Alger Hiss and the Rosenbergs were spies.
Contradiction: There is no suggestion that the Rosenbergs were spies.