Which early 20th century advertising campaign revolutionized product marketing by being the first to use testimonials from doctors to establish credibility?

Throughout history, product advertising has evolved dramatically, reflecting changing societal values and technological capabilities. The early 20th century saw some particularly innovative advertising campaigns that transformed how products were marketed forever. Test your knowledge about a groundbreaking historical advertising campaign that changed the retail landscape and set standards for future marketing strategies.

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Lucky Strike cigarettes' "20,679 physicians say Luckies are less irritating" campaign (1929)
Coca-Cola's "Drink Coca-Cola and enjoy it" physician endorsement ads (1917)
Ivory Soap's "99 and 44/100% pure, recommended by medical experts" campaign (1910)
Kellogg's Corn Flakes' "Doctor-approved breakfast for digestive health" campaign (1925)