Nash-Williams (1963). It has since become a prominent example in reversemathematics(英语:reversemathematics) as a statement that cannot be proved within ATR0 (a form
"Inversion Vector" (页面存档备份,存于互联网档案馆) From MathWorld--A Wolfram Web Resource Reverse colex order of finitary permutations (OEIS數列A055089) Aigner, Martin. Word