Following Planck, other German physicists quickly became interested in relativity, including Arnold Sommerfeld, Wilhelm Wien, Max Born, Paul Ehrenfest, and Alfred Bucherer. von Laue, who learned about the theory from Planck, published the first definitive monograph on relativity in 1911. By 1911, Sommerfeld altered his plan to speak about relativity at the Solvay Congress because the theory was already considered well established.