Gosney and Popenoe's book was specifically referenced by officials in Nazi Germany in the creation of their own sterilization legislation in 1933 as having provided them with proof that sterilization programs could be safe and effective. According to a U.S. health official at the time who had just returned from a trip to Germany, "the leaders in the German sterilization movement state repeatedly that their legislation was formulated only after careful study of the California experiment." (quoted in Kühl 1994, p. 42-43) Gosney and Popenoe believed the population of mentally ill in the United States could be reduced by half in "three or four generations." The Sacramento philanthropist/eugenicist Charles Goethe wrote to Gosney in a letter from 1934:  A follow-up study, "Twenty-eight Years of Sterilization in California" was published by the pair in 1938 (the "American Journal of Sociology" reviewed it with a single sentence: "An awkward attempt to popularize the practice of sterilizing defectives"). The state of California would eventually sterilize over 20,000 patients in state-run hospitals under its eugenic laws; Nazi Germany would sterilize over 400,000. In 1926, Gosney first began to organize what would by 1928 become chartered as the Human Betterment Foundation as a philanthropic foundation to promote research and advocacy of eugenics, especially by means of sterilization. As Gosney put it, the Foundation would work for: The initial board of trustees was Gosney, Henry M. Robinson (a Los Angeles banker), George Dock (a Pasadena physician), David Starr Jordan (chancellor of Stanford University), Justin Miller (dean of the college of law at the University of Southern California), Otis Castle (a Los Angeles attorney), Joe G. Crick (a Pasadena horticulturist), Goethe, and Popenoe. Later members included Lewis Terman (a Stanford psychologist best known for creating the Stanford-Binet test of IQ), William B. Munro (a Harvard professor of political science), and University of California, Berkeley professors Herbert M. Evans (anatomy) and Samuel J. Holmes (zoology). The Foundation also established links with the California Institute of Technology, with Nobel Prize-winning Caltech physicist Robert Millikan joining the board of the HBF in 1937. The Foundation published a number of pamphlets and financed continued studies of the California sterilization program through the 1930s, and sent thousands of letters to teachers, libraries, and physicians advocating eugenic sterilization.