  ROSAT spectra of 11 supersoft X-ray sources (RX J0439.8-6809, RX
J0513.9-6951, RX J0527.8-6954, CAL 87, CAL 83, 1E 0035.4-7230, RX J0048.4-7332,
1E 0056.8-7154, RX J0019.8 +2156, RX J0925.7-4758, AG Draconis) are
approximated with theoretical spectra obtained in LTE models for the
atmospheres of hot white dwarfs with line blanketing. The confidence intervals
of parameters derived from these approximations $ T_{\rm eff}$, $\log g$,
$N_H$, and $R^2/d^2$ are determined. The results are compared with predictions
for a model with stable/recurrent thermonuclear burning on the white-dwarf
surface.
