Another author, cited by Callen as giving a "scholarly and rigorous treatment", and cited by Adkins as having written a "classic text", A.B. Pippard writes in that text: "Given long enough a supercooled vapour will eventually condense,.... The time involved may be so enormous, however, perhaps 10 years or more,.... For most purposes, provided the rapid change is not artificially stimulated, the systems may be regarded as being in equilibrium."