Kaufmann–Bucherer–Neumann experiments : To conclusively decide between the theories of Abraham and Lorentz, Kaufmann repeated his experiments in 1905 with improved accuracy. However, in the meantime the theoretical situation had changed. Alfred Bucherer and Paul Langevin (1904) developed another model, in which the electron is contracted in the line of motion, and dilated in the transverse direction, so that the volume remains constant. While Kaufmann was still evaluating his experiments, Einstein published his theory of special relativity. Eventually, Kaufmann published his results in December 1905 and argued that they are in agreement with Abraham's theory and require rejection of the "basic assumption of Lorentz and Einstein" (the relativity principle). Lorentz reacted with the phrase "I am at the end of my Latin", while Einstein did not mention those experiments before 1908. Yet, others started to criticize the experiments. Max Planck (1906) alluded to inconsistencies in the theoretical interpretation of the data, and Adolf Bestelmeyer (1906) introduced new techniques, which (especially in the area of low velocities) gave different results and which cast doubts on Kaufmann's methods. Therefore, Bucherer (1908) conducted new experiments and arrived at the conclusion that they confirm the mass formula of relativity and thus the "relativity principle of Lorentz and Einstein". Yet Bucherer's experiments were criticized by Bestelmeyer leading to a sharp dispute between the two experimentalists. On the other hand, additional experiments of Hupka (1910), Neumann (1914) and others seemed to confirm Bucherer's result. The doubts lasted until 1940, when in similar experiments Abraham's theory was conclusively disproved. (It must be remarked that besides those experiments, the relativistic mass formula had already been confirmed by 1917 in the course of investigations on the theory of spectra. In modern particle accelerators, the relativistic mass formula is routinely confirmed.)