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

The intrinsic variations of bright stars in NGC 7160Mars, Mario; Aas, Toomas; Harvig, VoldemarBinaries-Key to Comprehension of the Universe, Masaryk University, Brno, Czech Republic, 8–12 June 20092010 / p. 131-134 https://www.researchgate.net/publication/252384047_The_Intrinsic_Variations_of_Bright_Stars_in_NGC_7160