However its impact has been far greater than that. Armed with this idea and inspired by Vannevar Bush's famous article "As We May Think", Eugene Garfield at the Institute for Scientific Information in the 1960s developed a comprehensive index of how scientific thinking propagates. His Science Citation Index (SCI) had the effect of making it easy to identify exactly which scientists did science that had an impact, and which journals that science appeared in. It also caused the discovery, which some did not expect, that a few journals, such as "Nature" and "Science", were core for all of hard science. The same pattern does not happen with the humanities or the social sciences.