Czech serologist Jan Janský independently introduced blood type classification in 1907 in a local journal. He used the Roman numerical I, II, III, and IV (corresponding to modern O, A, B, and AB). Unbeknown to Janský, an American physician William L. Moss devised a slightly different classification using the same numerical; his I, II, III, and IV corresponding to modern AB, A, B, and O. These two systems created confusion and potential danger in medical practice. Moss's system was adopted in Britain, France, and US, while Janský's was preferred in most European countries and some parts of US. To resolve the chaos, the American Association of Immunologists, the Society of American Bacteriologists, and the Association of Pathologists and Bacteriologists made a joint recommendation in 1921 that the Jansky classification be adopted based on priority. But it was not followed particularly where Moss's system had been used. In 1927, Landsteiner, who had moved to the Rockefeller Institute for Medical Research in New York, and as a member of a committee of the National Research Council concerned with blood grouping suggested to substitute Janský's and Moss's systems with the letters O, A, B, and AB. (There was another confusion on the use of figure 0 for German "null" as introduced by Hirszfeld and von Dungern, because others used the letter O for "ohne", meaning without or zero; Landsteiner chose the latter.) This classification was adopted by the National Research Council and became variously known as the National Research Council classification, the International classification, and most popularly the "new" Landsteiner classification. The new system was gradually accepted and by the early 1950s, it was universally followed.