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Zeitreihen 1950 - 1991. - 1993. - 263 S.
Noll, Heinz-Herbert, (1993)
Potential and availability of market research data for empirical social and economic research
Wiegand, Erich, (2009)
Das grosse Buch des Wissens : Lexikon in Wort u. Bild
Wiegand, Erich, (1959)