In this paper we show that a connected graph of order n, radius r and minimum degree delta has at least 1/2 (delta n + (n-1)(delta-2)/(delta-1)(r)-1) edges, for n large enough, and this bound is sharp. We also present a similar result for digraphs. (C) 2009 Elsevier B.V. All rights reserved.
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Yuncheng Univ, Sch Math & Informat Technol, Yuncheng 044000, Peoples R China
Xinjiang Univ, Coll Math & Syst Sci, Urumqi 830046, Peoples R ChinaYuncheng Univ, Sch Math & Informat Technol, Yuncheng 044000, Peoples R China
Hu, Yarong
Huang, Qiongxiang
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Xinjiang Univ, Coll Math & Syst Sci, Urumqi 830046, Peoples R ChinaYuncheng Univ, Sch Math & Informat Technol, Yuncheng 044000, Peoples R China
Huang, Qiongxiang
Lou, Zhenzhen
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Univ Shanghai Sci & Technol, Coll Sci, Shanghai 200093, Peoples R ChinaYuncheng Univ, Sch Math & Informat Technol, Yuncheng 044000, Peoples R China
机构:
E China Normal Univ, Dept Math, Shanghai 200241, Peoples R ChinaE China Normal Univ, Dept Math, Shanghai 200241, Peoples R China
Xu, Mimi
Hong, Yuan
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E China Normal Univ, Dept Math, Shanghai 200241, Peoples R ChinaE China Normal Univ, Dept Math, Shanghai 200241, Peoples R China
Hong, Yuan
Shu, Jinlong
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E China Normal Univ, Dept Math, Shanghai 200241, Peoples R China
E China Normal Univ, Shanghai Key Lab Trustworthy Comp, Shanghai 200062, Peoples R ChinaE China Normal Univ, Dept Math, Shanghai 200241, Peoples R China
Shu, Jinlong
Zhai, Mingqing
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E China Normal Univ, Dept Math, Shanghai 200241, Peoples R China
Chuzhou Univ, Dept Math, Chuzhou 239012, Anhui, Peoples R ChinaE China Normal Univ, Dept Math, Shanghai 200241, Peoples R China