The Light-Time Effect in the Eclipsing Binaries GK Cep and VY Cet
  New times of minima of the eclipsing binaries GK Cep and VY Cet, obtained at the Observatory of the University of Athens, have been used together with all reliable timings found in the literature in order to study the period variation and search for the presence of third body in the systems. 
Alexios Liakos and Panagiotis Niarchos
astro-ph.SR