Chao's 1984 estimator explicitly extends Harris's (1959) occupancy bound, not an independent derivation

Anne Chao's 1984 paper positions its own method as a direct methodological descendant rather than a fresh invention: "The method is similar to that taken by Harris (1959). We first estimate En₀, the expected value of the number of unobserved classes. Harris (1959) proved that for r = d(N), [bound follows]." Harris's 1959 "Determining bounds on integrals with applications to cataloging problems" (Ann. Math. Statist. 30, 521–548) supplies the underlying asymptotic occupancy bound; Chao and, before her, Cobb & Harris (1966) reused the same distribution-function approach for other statistical problems before Chao applied it to the unseen-species count.

The paper also shows its own estimator, under a polynomial rather than distribution-function approximation, collapses exactly onto a competing estimator: "we obtain exactly the jackknife estimator given in (1). Thus this approach also provides a justification of the use of the jackknife estimator" — crediting Burnham & Overton's (1978, 1979) prior jackknife method as a special case her more general method recovers. The 1984 paper is therefore one point in an explicit lineage — Harris (1959) → Cobb & Harris (1966) → Burnham & Overton (1978/1979) → Chao (1984) — not, as the Good-Turing/Chao1 pairing sometimes reads informally, a second independent route to the same object as Good and Turing's wartime derivation.