experiments were regarded as decisive. But it was shown in 1938 that all those experiments of Kaufmann, Bucherer, Neumann etc. showed only a qualitative increase in mass, but were too imprecise to distinguish between the different models. This lasted until 1940, when similar experimental equipments were sufficiently accurate to confirm the Lorentz-Einstein formula, see Kaufmann–Bucherer–Neumann experiments and Tests of relativistic energy and momentum. Bucherer (1906) was the first who used — during some critical remarks on Einstein's theory — the expression "Einsteinian relativity theory / theory of relativity" ("Einsteinsche Relativitätstheorie"). This was based on Max Planck's term "relative theory" for the Lorentz-Einstein theory. And in 1908 Bucherer himself rejected his own version of the relativity principle, and accepted the "Lorentz-Einstein theory". Later (1923, 1924), Bucherer criticized general relativity in some papers. However, this criticism was rejected because Bucherer misinterpreted Einstein's equivalence hypothesis. See also History of special relativity Sources Publications 1863 births 1927 deaths 20th-century German physicists Mass spectrometrists Fellows of the American Physical Society 19th-century German physicists