Ruggles, Richard; Brodie, Henry (1947), «An empirical approach to economic intelligence in WWII», American Statistical Association, Journal of the American Statistical Association, 42 (237): 72–91, JSTOR2280189, doi:10.2307/2280189
Ruggles, Richard; Brodie, Henry (1947), «An empirical approach to economic intelligence in WWII», American Statistical Association, Journal of the American Statistical Association, 42 (237): 72–91, JSTOR2280189, doi:10.2307/2280189