Analysis of information sources in references of the Wikipedia article "Permutation" in English language version.
It is customary to use lowercase Greek letters (especially π, σ, and τ) to stand for permutations.
Cauchy used his permutation notation—in which the arrangements are written one below the other and both are enclosed in parentheses—for the first time in 1815.
It is customary to use lowercase Greek letters (especially π, σ, and τ) to stand for permutations.