“…In 1933 Klemperer introduced the birth register method, followed by Fremming (1951) and Helgason (1964). The census method was used by Lewis (1929), Brugger (1931Brugger ( , 1933bBrugger ( , 1938, Matthews et al (1937), Stromgren (1938), Lemkau et al (1941Lemkau et al ( , 1942aLemkau et al ( , b, 1943, Kaila (1942), Bremer (1951), Book (1953), and Essen-Moller (1956). A more detailed discussion on method, selection of proband material, and results of these studies is found in the monographs by Akesson (1961,1968), and Wallin (1974).…”