In the 1920s, slices of which crystalline mineral were first used to control radio frequencies?

Around 1914, which oil company became the first to give away free road maps to travelers? In 1915, Claude Debussy dedicated his 12 Études to the memory of which Polish-French composer? Around 1915, which Italian artist painted an elongated portrait of painter Juan Gris? Around 1916, newspaper columnist Don Marquis created which typing cockroach, a friend of Mehitabel the cat? Around 1927, which American artist known for his mobiles made a portrait of Josephine Baker out of wire? Around 1930, poet Angelos Sikelianos tried to revive the ancient festivals of which Greek town, called the "navel of th… Around 1930, William Lear helped develop which device for cars, sold under the name Motorola? Which nun moved into the slums of Calcutta around 1948 to help the poor and was beatified on October 19, 2003?