 Following on Liboff, Ghazi Hassoun and Donald Kobe (1989) have argued that in order to obtain a meaningful classical limit of quantum mechanical eigenvalues it is necessary that “both formulations [of the correspondence principle] are used concurrently in the sense that the Planck constant goes to zero and the appropriate quantum number goes to infinity … subject to the constraint that \(nh = J\), where \(J\) is the appropriate classical action” (Hassoun and Kobe 1989, p. 658). On this reading, Bohr’s correspondence principle is construed simply as the limit \(n \rightarrow \infty\). Although they call this limit “Bohr’s correspondence principle”, they note that Bohr was able to obtain the correct classical orbital frequency precisely “because he did not take the mathematical limit as the quantum number goes to infinity. Instead, Bohr considered that for large quantum numbers the quantum result was very nearly the classical result. Thus the quantum number \(n\), say, was \(n \gg 1\), but was not infinite” (Hassoun and Kobe 1989, p.  661). They conclude that the correspondence principle is “often thought to be imprecise because of Bohr’s use of large, but not infinite, quantum numbers. However, when the Bohr and Planck formulations are synthesized, as shown in this article, the correspondence principle has a precise mathematical form” (Hassoun and Kobe 1989, p. 661). The correspondence principle on this reading is understood broadly as the attempt to get a mathematically precise formulation of the classical limit.