  The celebrated quantum no-cloning theorem establishes the impossibility of
making a perfect copy of an unknown quantum state. The discovery of this
important theorem for the field of quantum information is currently dated 1982.
I show here that an article published in 1970 [J. L. Park, Foundations of
Physics, 1, 23-33 (1970)] contained an explicit mathematical proof of the
impossibility of cloning quantum states. I analyze Park's demonstration in the
light of published explanations concerning the genesis of the better-known
papers on no-cloning.
