Piet L. J. Hermkens (Hermkens, Piet L. J.)

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  via
  Solidarity of Generations: Demographic, Economic, and Social Change, and Its Consequences
  by H.A. Becker, Piet L. J. Hermkens
  Softcover, Purdue Univ Pr, ISBN 9051702604 (90-5170-260-4)