Nido R. Qubein (1996). “Achieving Peak Performance: A Step by Step System to Grow a Well Trained, Educated, and Motivated Team for the 21st Century”, Bestsellers Publishing
Man and Superman "Maxims for Revolutionists" (1903). A further extension appears in Jacob M. Braude, Speaker's Encyclopedia of Stories, Quotations, and Anecdotes (1955): "Those who can, do; those who can't teach; and those who can't do anything at all, teach the teachers."