简介:Itisprovedthatevery3-connectedlooplessmultigraphhasmaximumgenusatleastone-thirdofitscyclerankplusoneifitscyclerankisnotlessthanten,andifitscyclerankislessthanten,itisupper-embeddable.Thislowerboundistight.Thereareinfinitelymany3-connectedlooplessmultigraphsattainingthisbound.