• Light-time effect in selected semi-detached and contact binaries with observable third componentsPustõlnik, Izold; Kalv, Peep; Aas, Toomas; Harvig, Voldemar; Mars, MarioThe Light-time Effect in Astrophysics, Causes and Cures of O-C diagrams2005 / p. 321-330 https://articles.adsabs.harvard.edu/pdf/2005ASPC..335..321P