Before revision: The origins of this approach can be traced back to pioneering studies of the 1920s such as Thomas' and Znaniecki's " The Polish Peasant in Europe and America " and Mannheim's essay on the "Problem of generations".Elder, Glen H.; Monica Kirkpatrick Johnson and Robert Crosnoe: The Emergence and Development of Life Course Theory.
After revision: The origins of this approach can be traced back to pioneering studies of the 1920s such as William I. Thomas and Florian Znaniecki's The Polish Peasant in Europe and America and Mannheim's essay on the "Problem of generations".Elder, Glen H.; Monica Kirkpatrick Johnson and Robert Crosnoe: The Emergence and Development of Life Course Theory.