Key points are not available for this paper at this time.
This article appears in the following collection:Letters from the Past - A PRL Retrospective2008 marked PRL's 50th anniversary. As part of the celebrations a collection of milestone Letters was started. The collection contains Letters that have made long-lived contributions to physics, either by announcing significant discoveries, or by initiating new areas of research.
Ivar Giæver (1960) studied this question.