Wilcoxon, 1945, Individual Comparisons by Ranking Methods, Biometrics, 1, 80, 10.2307/3001968
Dunn, 1964, Multiple Comparisons Using Rank Sums, Technometrics, 6, 241, 10.1080/00401706.1964.10490181
Fix, 1955, Significance Probabilities of the Wilcoxon Test, Ann. Math. Statist., 26, 301, 10.1214/aoms/1177728547