Li, Ping et Liu, Gui Zhen, The connectivity and minimum degree of circuit graphs of matroids, Acta mathematica Sinica. English series (Print) , 26(2), 2010, pp. 353-360
Let G be the circuit graph of any connected matroid M with minimum degree .(G). It is proved that its connectivity .(G) . 2|E(M) . B(M)| . 2. Therefore .(G) . 2|E(M) . B(M)| . 2 and this bound is the best possible in some sense.