Source of Arthur Samuel's definition of machine learning Many people seem to agree that Arthur Samuel wrote or said in 1959 that machine learning is the "Field of study that gives computers the ability to learn without being explicitly programmed". 

For example the quote is contained in this page, that one and in Andrew Ng's ML course. Several articles also contain this quote, and the reference is always the following article, which doesn't actually contain the quote.

Samuel, A. L. (1959). Some studies in machine learning using the game of checkers. IBM Journal of research and development, 3(3), 210-229.

Is there a reliable source? Or is this actually not a quote, but rather an interpretation of Samuel's article?
The exact quote exists in neither the 1959 paper nor the 1967 paper (second version).

These are the closest quotes from the 1959 paper:


  A computer can be programmed so that it will learn to play a better
  game of checkers than can be played by the person who wrote the
  program.


And 


  Programming computers to learn from experience should eventually
  eliminate the need for much of this detailed programming effort.


Also, Wiki page of Arthur Samuel states that:


  He coined the term "machine learning" in 1959


and references the 1959 paper.

Either the quote is created as a gist of Arthur Samuel's 1959 paper, or it is said but not written by him. In my opinion, the former is more probable, since it is not even remotely mentioned in the 1967 paper.