Power spectra of the intensity fluctuations of CP 0834, AP 1237, and CP 1919 show features corre- sponding to long periodicities (P4 100 sec) and shorter periodicities (P3 5 sec). The period equation P4 = P1P3/P2 predicts a P4 which differs from these measurements by 50 and 340 percent for CP 0834 and CP 1919, respectively. The relative intensities and the widths of the spectral features corresponding to P3 and P4 vary with the time of observation. Analog records of CP 1133 and AP 1237 indicate that their P4 is the result of a periodic switching mechanism of short duration and with sharp boundaries. The circulating-plasma model must be quite complicated if it is to account for this diverse set of observations.