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Claim. I. Kříž, All trapezoids are Ramsey, Discrete Math. 108 (1992), no. 1--3, 59--62, cited as [Kr92] in the site's commentary on Problem 174. The paper proves that every trapezoid is Ramsey in the sense of Problem 174, where its abstract defines a trapezoid as a quadrilateral inscribed in a circle with two parallel sides; the cyclic hypothesis is part of the definition, and the title is not a claim about nonspherical trapezoids, which Theorem 13 of the 1973 paper on its claim page excludes. The four-page proof is not reconstructed in the library and the paper has no library card. Behague's 2025 preprint gives a second proof for the nondegenerate convex reflection-symmetric isosceles trapezia, including rectangles, by a subsoluble enclosure, recorded on the problem page.

Covers. The class of cyclic trapezoids, the isosceles trapezia: each is Ramsey. The paper decides no other quadrilateral; the full classification is OpenAI's accepted claim.

Depends on. No page of this wiki.

Acceptance. Refereed: the paper is a journal publication in Discrete Mathematics, volume 108, issues 1--3 (October 1992), the refereed evidence; the issue carries no day, so this page is dated to the first day of that month. The site's curator credits trapezoids to [Kr92] in the problem's commentary, but the site labels the problem OPEN, so that credit is not reviewed evidence. The statement is taken from the published abstract; the proof is not checked by this corpus, and nothing is independently reviewed by this project.