In the 1960s, James Van Allen's Outer Planets Panel made a proposal that NASA begin planning missions to the outer planets, that eventually led to Pioneer 10 and 11. I've found many sources that mention it briefly. This one is characteristic:
During this same period an Outer Planets Panel associated with NASA's Lunar and Planetary Missions Board (also chaired by Van Allen) recommended in 1962 that planning should start for low-cost exploratory missions to the outer planets.
Does the text of this recommendation survive? What exactly did they say?