On 2-factors in star-free graphs

In this paper we give a sharp minimum degree condition for a 2-connected star-free graph to have a 2-factor containing specified edges. Let G be a 2-connected K _1,n-free graph with minimum degree n + d and I ⊂ E(G). If one of the followings holds, then G has a 2-factor which contains every edge in I: i) n = 3, d ≥ 1, |I| ≤ 2 and |V(G)| ≥ 8 if |I| = 2; ii) n = 4, d ≥ 1, |I| ≤ 2 and |V(G)| ≥ 11 if |I| = 2; iii) n ≥ 5, d ≥ 1 and |I| ≤ 1; iv) n ≥ 5, d ≥ [(√4n - 3 + l)/2] and |I| ≤ 2.