1. Cheng, Y.: Finite groups based on the numbers of elements of maximal order (in Chinese). Chinese Ann. Math. Ser. A 14(5), 561–567 (1993)
2. Youyi, J.: Finite groups with the number not exceeding 19 of elements of maximal order are solvable (in Chinese). J. Southwest China Normal Univ. (Natural Science Edition) 23(4), 379–384 (1998)
3. Youyi, J.: Finite groups with 2p 2 elements of maximal order are solvable (in Chinese). Chin. Ann. Math., A 21(1), 61–64 (2000)
4. He, C.: Finite groups with 2m ( $(m,\ 30)=1$ ) elements of maximal order. J. Southwest China Normal Univ. (Natural Science Edition) 29(3), 351–353 (2004)
5. Williams, J.S.: Prime graph components of finite groups. J. Algebra 69, 487–513 (1981)