Edward N. Luttwak, From Geopolitics to Geo-Economics: Logic of Conflict, Grammar of Commerce, The National Interest, No. 20 (Summer 1990), pp. 17-23 ...

Herbert A. Simon, A Behavioral Model of Rational Choice, The Quarterly Journal of Economics, Vol. 69, No. 1 (Feb., 1955), pp. 99-118 ...

The article discusses a model of accent mobility and provides data to support its findings.

T. H. Gronwall, Note on the Derivatives with Respect to a Parameter of the Solutions of a System of Differential Equations, Annals of Mathematics, Vol. 20, No. 4 (Jul., 1919), pp. 292-296 ...