This directory contains Extrem Ultraviolet (EUV) reference spectra and related EUV model parameters based on the measurements and work of H.E. Hinteregger and his colleagues. The model and reference spectra (R74113, F74113, F76REF, SC21REFW) are described by Hinteregger et al. (Geophys. Res. Lett. 8, 1147, 1981). The spectra and model are based on rocket measurements and simultaneously obtained EUV fluxes by the AE-C and AE-E spectrometer. The rocket measurements were used to establish absolute calibration factors for the AE-E instrument. The originally proposed R74113 spectrum (Hinteregger, J. Atmos. Terr. Phys. 38, 701, 1976) is based on AE-C measurements and data from a rocket flight on April 23, 1974. R74113 was revised to become F74113 (Heroux and Hinteregger, J. Geophys. Res. 83, 5305, 1978), following refined evaluation of the rocket and satellite data. F76REF used in addition AE-E data from July 13-28, 1976 (when solar activity was low and constant). SC21REFW extends F76REF to include a rocket flight on August 14, 1979. The F76REF and SC21REFW files include also the wave-length dependent adjustment factors that are used in Hinteregger's flux model. See also the explanations by the PI Hans Hinteregger in the file ../ae_e_euv_flux/Hinteregger_explanation_SC21.pdf.