Erratum.
In equation 6 of the Research Article "Effects of age on dopamine and seratonin receptors measured by positron tomography in the living human brain" by D. F. Wong et al. (21 Dec., p. 1393) C(p)(t) in the denominator of the last term should have been A(cb)(t). This does not affect the rest of the derivation. In the caption of figure 1, the first word, "Decrease," should have been "Change." The data in parts A and B of figure 3 should have been regraphed on common axes to facilitate comparison. A corrected figure 3 is shown below.