James E. Meade 
A Geometry of International Trade (Routledge Revivals) [PDF ebook] 

First published in 1952, this work is a systematic exposition of Professor Meade’s geometric method, bringing together into a single coherent account the modern geometrical analysis of the theory of international trade. The work makes a number of original contributions, notably in the geometrical treatment of domestic production, of the balance of payments, and of import and export duties.