Conference of the NATO-Advanced-Study-Institute on Variable Stars as Essential Astrophysical Tools, CESME, Türkiye, 31 Ağustos - 10 Eylül 1998, cilt.544, ss.605-614
The nature of the long-term period variations obtained by using the well known (O-C) method, of some classical algols were checked by forming independent period-time diagrams. It was shown that the (O-C) method works well in all cases for these systems.