Dear Dr Kato With regard to your recent analyses of visual observations: AAVSO have just recently made their GK Per data available as Monograph 13 [via their website]. It would be interesting if, using your techniques, you could recover the orbital period of this object from that data for the epochs of quiescence. I managed such once with less extensive BAAVSS data for this object, but was unable to ascertain whether or not the asymmetric nature of the folded lightcurve was meaningful or not. John JG, UK