Sunflower Lemma (Erdos-Rado 1960) 1F>(r-1)k> a sunflower gCF,such that g=r 3x∈Y,lett={S\{x}|S∈F∧x∈S ∈() 17H>(k-1)(r-1)k-1 I.H.:H contains a sunflower of size r adding x back,it is a sunflower inF ∃ x∈Y, H = {S \ {x} | S ￾ F ⌅ x ￾ S} H ⇥ ￾ [n] k ￾ 1 ⇥ let |H| > (k ￾ 1)!(r ￾ 1)k￾1 I.H.: H contains a sunflower of size r adding x back, it is a sunflower in F F ￾ ￾[n] k ⇥ . |F| > k!(r ￾ 1)k Sunflower Lemma (Erdős-Rado 1960) ⇥ a sunflower G ￾ F, such that |G| = r