"There are certain formal similarities between the problems of devising policies for economic stabilisation and those of designing automatic control systems. Methods have recently been developed by engineers for analysing the dynamic properties of quite complex models... [which] can also be used for the analysis of dynamic process models in economics... Professor Tustin’s book contains material of fundamental importance for all who are engaged in either theoretical or empirical studies of dynamic processes in economics. It throws new light on the possibilities and the difficulties of quantitative research in this field."