In the United States, the 1950s and 1960s saw the introduction of several large popular encyclopedias, often sold on installment plans. The best known of these were "World Book" and "Funk and Wagnalls". As many as 90% were sold door to door. Jack Lynch says in his book "You Could Look It Up" that encyclopedia salespeople were so common that they became the butt of jokes. He describes their sales pitch saying, "They were selling not books but a lifestyle, a future, a promise of social mobility." A 1961 "World Book" ad said, "You are holding your family’s future in your hands right now," while showing a feminine hand holding an order form.