Follow the ideas, results and limitations over time. This is a selected history, not a complete literature survey or a measure of how close the problem is to being solved.
The published proceedings introduce the broader cycle-algebraicity question. The modern record uses rational coefficients and smooth projective varieties.
Scope & review: 1952 is the proceedings publication year, not a precise formulation date or an established theorem.
Historical annotation review: pending. The date refers to the publication, with the precision supported by the source.
publication
Special case proved
The divisor-class criterion in the cited exposition
The Kodaira–Spencer account cited by Deligne records the Lefschetz (1,1) theorem, the codimension-one foundation.
Scope & review: This is the cited exposition’s date, not a claim of first discovery. Higher codimension does not follow merely by multiplying divisors.
Historical annotation review: pending. The date refers to the preprint, with the precision supported by the source.
publication
Special case proved
A published geometric proof for selected powers
Floccari–Fu’s journal publication proves rational Hodge for every power of a Weil fourfold with discriminant 1; the cited author v2 fixes theorem text.
Scope & review: The discriminant and Weil-type hypotheses are essential. This is a publication event, not an assertion that the theorem first appeared in June.