Radiation protection continued to develop with the invention of new measuring devices such as the chromoradiometer by Guido Holzknecht (1872-1931) in 1902, the radiometer by Raymond Sabouraud (1864-1938) and Henri Noiré (1878–1937) in 1904/05, and the quantimeter by Robert Kienböck (1873-1951) in 1905, which made it possible to determine maximum doses at which there was a high probability that no skin changes would occur. Radium was also included by the British Roentgen Society, which published its first memorandum on radium protection in 1921.