A number of Swedish researchers, Johanson, Wiedersheim-Paul and Vahlne, at the University of Uppsala studied the intemalisation process during the 1970s. They were influenced by Penrose's theory on the growth of the firm. The Uppsala model seeks to explain and predict two aspects of intemationalisation of the firm: the step-by-step pattern of industrial development within individual national markets and the expansion of companies across national markets, as they move from nations which are proximal to those which are increasingly psychically distant. Johanson, Wiedersheim-Paul and Vahlne studied the intemationalisation of Swedish manufacturing companies and developed a model of the companies' choice of market and form of entry when going abroad. It is a dynamic model that describes the internationalisation of the company as a process. They were also influenced by Aharoni's seminal study from 1966.