Geary, R. (1978). Excess of Craftsmen's Pay over that of the Unskilled Worker: An Aspect of the Rate of Interest, Memorandum Series 130, Dublin: ESRI, https://www.esri.ie/publications/excess-of-craftsmens-pay-over-that-of-the-unskilled-worker-an-aspect-of-the-rate-of-interest