We have determined the ephemeris from photoelectric minima times only in
the case of GW Car, because they covered the interval of 12 years. For other
stars we had to use also the published photographic minima times. We fitted
these data by linear ephemeris and found the standard error and corresponding
weight from the scatter of these data. Thereafter, we normalized the weights of
photoelectric data setting the weights of photographic data w = 1. All minima
times including their weights were used for determination of the ephemerides,
valid in the intervals covered by observations.