The pilot rating scale by George E. Cooper (the Cooper Rating Scale) improved by Robert P. Harper, Jr. as shown in their paper "The use of pilot rating in the evaluation of aircraft handling qualities", NASA-TN-D-5153 , April 1969.
George E. Cooper and Robert P. Harper, Jr.
1969-04
<a rel="nofollow" class="external free" href="https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690013177.pdf">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690013177.pdf</a> page 12