Karl Pearson: On the criterion that a given system of derivations from the probable in the case of a correlated system of variables is such that it can be reasonably supposed to have arisen from random sampling. In: The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science. Band50, Nr.5, 1900, S.157–175, doi:10.1080/14786440009463897.
Student: The Probable Error of a Mean. In: Biometrika. Band6, Nr.1, 1908, S.1–25, doi:10.2307/2331554.
R. A. Fisher: On the mathematical foundations of theoretical statistics. In: Philosophical Transactions of the Royal Society. A 222, 1922, S.309–368, doi:10.1098/rsta.1922.0009.