Polonium in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphate fertilizers. Because it is present in small concentrations, isolation of polonium from natural sources is a tedious process. The largest batch of the element ever extracted, performed in the first half of the 20th century, contained only (9 mg) of polonium-210 and was obtained by processing 37 tonnes of residues from radium production. Polonium is now usually obtained by irradiating bismuth with high-energy neutrons or protons. In 1934, an experiment showed that when natural Bi is bombarded with neutrons, Bi
Discover Card card was used. A 1989 study found that Discover had strong consumer adoption in the U.S.; the number of households with Discover cards increased by 2.1 million, or 14 percent, in 1989. Discover was also noteworthy for being the only credit card accepted by the U.S. Customs Service to pay customs duty, effective Feb. 19, 1987. Since it did not charge a percentage fee to retailers, unlike Visa, MasterCard, and American Express, Discover was also the only credit card accepted at Sam's Club; the retailer has since started to accept MasterCard and American Express (see below). The plan to create