Source: The Art of Probability for Scientists and Engineers (1991), p. 4 [emphasis in original]
“There are too many experts, we lack true practitioners in marketing.”
Related quotes

North Korea Dear Leader Kim Jong Il: "I'm an Internet expert too", Ars Technica, 2007-10-05, 2008-01-01 http://arstechnica.com/news.ars/post/20071005-north-korea-dear-leader-kim-jong-il-im-an-internet-expert-too.html,

“In the beginner's mind there are many possibilities, in the expert's there are few.”
Prologue
Zen Mind, Beginner's Mind (1973)
Variant: In the beginner’s mind there are many possibilities, but in the expert’s there are few
Source: Zen Mind, Beginner's Mind: Informal Talks on Zen Meditation and Practice

“When we know and love the best we are content to lack the approval of the many.”
Source: Aphorisms and Reflections (1901), p. 171

As quoted in Dynamic Work Simplification (1971) by W. Clements Zinck, p. 122
To create a high performing team the key is to align all members of your team so that each member is moving in the same direction and understands their role and contribution. A good analogy is to think of a team of rowers where if the each rower is not totally aligned with all the other rowers the boat might go around in circles or even capsize.
page 190
Your Job-Hunt Ltd – Advice from an Award-Winning Asian Headhunter (2003), Successful Recruitment in a Week (2012) https://books.google.ae/books?id=p24GkAsgjGEC&printsec=frontcover&dq=nigel+cumberland&hl=en&sa=X&ved=0ahUKEwjF75Xw0IHNAhULLcAKHazACBMQ6AEIGjAA#v=onepage&q=nigel%20cumberland&f=false, Managing Teams in a Week (2013) https://books.google.ae/books?id=qZjO9_ov74EC&printsec=frontcover&dq=nigel+cumberland&hl=en&sa=X&ved=0ahUKEwjF75Xw0IHNAhULLcAKHazACBMQ6AEIIDAB#v=onepage&q=nigel%20cumberland&f=false, Secrets of Success at Work – 50 techniques to excel (2014) https://books.google.ae/books?id=4S7vAgAAQBAJ&printsec=frontcover&dq=nigel+cumberland&hl=en&sa=X&ved=0ahUKEwjF75Xw0IHNAhULLcAKHazACBMQ6AEIJjAC#v=onepage&q=nigel%20cumberland&f=false

Source: Andreas Mogensen (2021) cited in " These astronauts will be able to unlock Mars’ secrets by looking at rocks on Earth https://www.euronews.com/next/2021/12/14/these-astronauts-will-be-able-to-unlock-mars-secrets-by-looking-at-rocks-on-earth" on Euro News, 14 December 2021.

“Learning is, in too many cases, but a foil to common sense; a substitute for true knowledge.”
"On the Ignorance of the Learned"
Table Talk: Essays On Men And Manners http://www.blupete.com/Literature/Essays/TableHazIV.htm (1821-1822)

"Ray Bradbury hates big government: ‘Our country is in need of a revolution’" in The Los Angeles Times : Hero Complex (16 August 2010) http://herocomplex.latimes.com/2010/08/16/ray-bradbury-is-sick-of-big-government-our-country-is-in-need-of-a-revolution/

“That is the judgment of our Nuclear Regulatory Commission and many other experts.”
2011, Address on the natural and nuclear energy disasters in Japan (March 2011)
Context: I know that many Americans are also worried about the potential risks to the United States. So I want to be very clear: We do not expect harmful levels of radiation to reach the United States, whether it’s the West Coast, Hawaii, Alaska, or U. S. territories in the Pacific. Let me repeat that: We do not expect harmful levels of radiation to reach the West Coast, Hawaii, Alaska, or U. S. territories in the Pacific. That is the judgment of our Nuclear Regulatory Commission and many other experts.