@article {Estimating1985,
title = {Estimating Regression Equations with Common Explanatory Variables but Unequal Numbers of Observations},
year = {1985},
url = {https://www.esri.ie/publications/estimating-regression-equations-with-common-explanatory-variables-but-unequal-numbers-of-observations},
author = {Conniffe, Denis},
journal = {Journal of Econometrics, Vol. 27, 1985},
}