  A commentary is made on the recent work by Cardy, ArXiv:1603. 08267, on
quantum revivals and higher dimensional CFT. The actual expressions used here
are those derived some time ago. The calculation is extended to fermion fields
for which the power spectrum involves the odd divisor function. Comments are
made on the equivalence of operator counting and eigenvalue methods, which is
quickly verified. An explanation of the rational revivals for odd spheres is
given in terms of wrongly quantised fields.
