\input zb-basic \input zb-ioport \iteman{io-port 06023653} \itemau{Hu, Maolin; Cheng, Yongxi; Xu, Weidong} \itemti{A generalization of Boesch's theorem.} \itemso{Discrete Math. 312, No. 6, 1171-1177 (2012).} \itemcc{} \itemut{network reliability; Boesch's theorem; $t$-optimal graphs; spanning trees} \itemli{doi:10.1016/j.disc.2011.12.001} \end