1. Alfred Clark, ‘Mass Leisure: A New Social Problem’, Water Quality and Recreation, (Columbus, Ohio: Ohio State University Press, 1966) pp. 23–37.
2. A comprehensive review of several methods of estimating demand for outdoor recreation and a convincing example of a demand function derived from a ‘willingness to pay’ analysis is given by, J. L. Knetsch and R. Davis, ‘Comparisons of Methods for Recreation Evaluation’, A. V. Kneese and S. C. Smith Water Research, (Baltimore: Johns Hopkins Press, 1967) pp. 125–42.