  I point out that the results stated in the recent articles on photon
splitting by Wunner, Sang, and Berg and by Wentzel, Berg, \& Wunner directly
contradict an earlier analytic and numerical calculation that I performed of
the same process using Schwinger's proper time method, for strong magnetic
fields and general energies below the pair production threshold. The results of
Wunner et al. and Wentzel et al. do not show the expected low frequency
behavior, nor have they been able to reproduce the expected small magnetic
field behavior, suggesting that their calculations may not be gauge invariant.
