 A Bayesian Analysis of Some Nonparametric Problems by Thomas S. Ferguson

By Thomas S. Ferguson. The Annals of Statistics 1(2), 209–230.

Original paper: users.wpi.edu/~balnan/Ferguson1973.pdf

Sections 3–4 define the Dirichlet process and its discrete realization; Section 3, Theorem 1, gives the posterior update by adding point masses at observations. The wiki uses concentration plus a normalized base measure instead of the paper's single finite nonzero parameter measure.