Claims

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1979_01_01_khadzhiivanov_nikiforov: Khadzhiivanov and Nikiforov's 1979 theorem, proved in full in Khadzhiivanov's 1988 account, that more than n²/4 edges force an edge on at least n/6 triangles, so in Problem 80 the forced book is linear above density 1/4.

2011_06_01_fox_loh: Theorem 1.1 of Fox and Loh (Combinatorica 2012): for every fixed density below one quarter the largest forced book is n to the o(1), so the first closing question of Problem 80 is answered no; refereed.

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