Being: Mass, Ether, and the Unification of Forces (New York: Basic Books, 2008). Whittaker, Edmund T, A History of the Theories of Aether and Electricity: From the Age of Descartes to the Close of the Nineteenth Century (London, New York, Bombay, Calcutta: Longmans, Green, and Co, 1910 / Dublin: Hodges, Figgis, & Co, 1910). Wolfson, Richard, Simply Einstein: Relativity Demystified (New York: W W Norton & Co, 2003). Woodward, James, "Scientific explanation", in Edward N Zalta, ed, The Stanford Encyclopedia of Philosophy, Winter 2011 edn. Wootton, David, ed, Modern Political Thought: Readings from Machiavelli to Nietzsche (Indianapolis: Hackett Publishing, 1996). Further reading Carl G. Hempel, Aspects of Scientific Explanation and other Essays in the Philosophy of Science (New York: Free Press, 1965). Randolph G. Mayes, "Theories of explanation", in Fieser Dowden, ed, Internet Encyclopedia of Philosophy, 2006. Ilkka Niiniluoto, "Covering law model", in Robert Audi, ed., The Cambridge Dictionary of Philosophy, 2nd edn (New York: Cambridge University Press, 1996). Wesley C. Salmon, Four Decades of Scientific Explanation (Minneapolis: University of Minnesota Press, 1990 / Pittsburgh: University of Pittsburgh Press, 2006). Scientific method Philosophy of science Conceptual models