This paper describes the background and objectives of a series of papers written fifty years ago at the London School of Economics (LSE). One objective was to encourage the use of accounting numbers in economic research. A second objective was to improve the theory and practice of accounting. Understanding cost accounting and opportunity costs within a firm was tied to understanding the organization of firms. The theory of the accounting system is part of the theory of the firm. Like a similar request made fifty years ago, the paper concludes with a call for interdisciplinary studies between economics and accounting.