If the parallax stars are arranged according to their apparent proper motion, or even according to their absolute proper motion, a similar Bipartition is revealed in their frequency distribution.
"Lectures on Stellar Statistics"
Carl Vilhelm Ludvig Charlier
Such an apparent Bipartition is, indeed, necessary in all statistics as soon as individuals are selected from a given population in such a manner as the parallax stars are selected from the stars in space.
"Lectures on Stellar Statistics"
Carl Vilhelm Ludvig Charlier