FR2128078-A  "TECHNISCHE MITTELLUNGEN AEG-TELEFUNKEN",VOL 60,1970,NO 2,"DAS ENERGIEVERSORGUNGSSYSTEM DES;  "THIN FILM SOLAR CELLS FOR BALLOON APPLICATIONS",F.A.SHIRLAND,PAGES 804;  (REVUE AMERICAINE"PROCCEDINGS OF THE INSTRUMENT SOCIETY OF AMERICA"VOL 23,28-31 OCTOBRE 1968. "THIN FILM SOLAR CELLS FOR BALLOON APPLICATIONS",F.A.SHIRLAND,PAGES 804;  *REVUE ALLEMANDE "TECHNISCHE MITTELLUNGEN AEG-TELEFUNKEN",VOL 60,1970,NO 2,"DAS ENERGIEVERSORGUNGSSYSTEM DES ERSTEN DEUTSCHEN FORSCHUNGSSATELLITEN AZUR",P.PAULSEN,PAGES 83-84.);  1-5.;  ERSTEN DEUTSCHEN FORSCHUNGSSATELLITEN AZUR",P.PAULSEN,PAGES 83-84.);  REVUE ALLEMANDE;  REVUE AMERICAINE"PROCCEDINGS OF THE INSTRUMENT SOCIETY OF AMERICA"VOL 23,28-31 OCTOBRE 1968.
US3980497-A  Ott et al., Cellulose and Cellulose Derivatives, Second Edition, by Interscience Publishers, Inc. N.Y., (1954), pp. 202-207.