EntityQ954454· pop 18· linked from 33 articleshandshaking lemmaSign in to savelemma that every node-link graph has an even number of odd-degree verticesConnectionsnodeEntityEulerian pathEntitypathEntityglossary of graph theory termsEntityLeonhard EulerEntityInternational Standard Book NumberEntityKaliningradEntitydigital object identifierEntityparallelogramEntityhexagonEntitygraph theoryEntityparityEntitymathematical inductionEntitygraphEntityJSTOROrganizationQ118398EntitySeven Bridges of KönigsbergEntitycardinalityEntityNash equilibriumEntitytravelling salesperson problemEntityCategoriesLemmas in graph theory