Barcelona metro map for Developed countries also increasingly turned to non-OPEC oil exporters, such as Mexico and the Soviet Union. Conservation efforts increased in many countries, as many were forced to rethink the consumerism illustrated by high energy use. In addition, many industrialized countries explored and developed alternative sources of energy, such as nuclear power. Nevertheless, as prices steadily decreased after the oil shock, the world still depended a great deal on oil as the main source of energy. BIBLIOGRAPHY. Anthony Sampson, The Seven Sisters: The Great Oil Companies and the World They Made (Viking Penguin, 1975); Michael Economides, et al., The Color of Oil: The History, the Money and the Politics of the World’s Biggest Business (Round Oak Publishing, 2000); Roger Olien, Oil in Texas: The Gusher Age, 1895 1945 (University of Texas Press, 2002); Steven Topik and Allen Wells, The Second Conquest of Latin America (University of Texas Press, 1998); John Wirth, ed. Barcelona metro map 2016.