 In his 1984 Physics Today article “The Correspondence Principle Revisited,” Richard Liboff argues that Bohr’s correspondence principle is not a general claim about recovering classical mechanics from quantum mechanics, but the following more restricted claim: “the quantum frequency spectrum of a periodic system approaches the classical spectrum in the limit of large \(n\)” (Liboff 1984, p. 52). Liboff goes on to note that even this restricted form of the correspondence principle is violated for systems such as a particle in a box and a rigid rotor. He notes that “[i]n both of these cases, the limit \(h \rightarrow 0\) leads to frequency correspondence, but the limit \(n \rightarrow \infty\) does not” (Liboff 1984, p. 52).