@article {Change1982,
title = {Change in a Produce between Two States as the Symmetrical Sum of Changes in Each of Its Factors},
year = {1982},
url = {https://www.esri.ie/publications/change-in-a-produce-between-two-states-as-the-symmetrical-sum-of-changes-in-each-of-its-factors},
author = {Geary, Roy C},
journal = {Memorandum Series 152},
}