The short range order data of Hanawalt (1931b) stimulated Kronig (1932) to develop a theory for molecules. This model served as the starting point for all the subsequent short range order theories but few attempted to compare it to their data. Kronig's student, H. Petersen (1932, 1933) continued this work. Peterson's equation shows many of the features of the modern theory. This theory was applied to GeCl4 by Hartree, Kronig and Petersen (1934). A description of the Herculean efforts required to perform the calculations can be found in Stumm von Bordwehr (1989).