Sample of plots of the O − C diagrams, full set of figures is in appendix section. Final fits of the apsidal motion are plotted as black and blue curves (for primary and secondary minima), while the individual points represent the times of eclipses. The larger the symbol, the higher the weight (which was assigned according to its uncertainty). New observations with DK154 are shown in red. In cases where an additional third body was found, the final fit is plotted (solid lines) together with only the apsidal motion fits (dashed lines).