Claims

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2022_07_25_wigderson: Answers the site's wording (every finite family), not the corrected Statement (every family other than a star with a matching), so it does not count toward the problem's standing. The two-edge star and the two-edge matching have joint extremal number 1 while each alone has linear extremal number; Wigderson's note records the folklore example.

2026_04_28_kj_c: A forum post claims that a family whose members all have linear extremal number has bounded extremal number exactly when it holds a star and a matching, and linear otherwise; unreviewed, with an unbuilt Lean development.

2026_08_01_openai: Theorem 1.1 of Chapter 10 of OpenAI's 2026 report gives a finite family of connected bipartite graphs with cycles whose joint extremal number is a power of n below every member's; the site's curator credits the disproof.

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