 It is perhaps for this reason that Jagdish Mehra and Helmut Rechenberg (1982), in their comprehensive history of the development of quantum theory, make no concrete commitment as to which of the several correspondence relations discussed by Bohr should be designated as the correspondence principle. Like Jammer they struggle to understand why Bohr thought the correspondence principle applied to small quantum numbers and why it should be considered a law of quantum theory. They write, “[T]he extension of the analogy ‘in some way’ to small quantum numbers represented a most daring assumption… [Bohr] felt confident that an extension of his relations for frequencies and intensities, which were valid in the high quantum number limit, might eventually be justified also when low quantum numbers were involved” (Mehra and Rechenberg 1982, p. 250). Although they offer one of the more technically detailed discussions of the correspondence principle, they do not discuss either Bohr’s claim that it should be considered a law nor Bohr’s claim that the correspondence principle is formalized into the new quantum mechanics.