The main challenge here lies in devising a mathematically acceptable proof of this impossibility, which is where the foundations for what we today know as graph theory.

D. B. West, Introduction to Graph Theory, Prentice Hall 2001 R. Diestel, Graph Theory, Springer 2010. N. L. Biggs, Discrete Mathematics, OUP 2004 J.A.Bondy and U.S.R. Murty, Graph Theory with ...

Abstractions blog A New Algorithm for Graph Crossings, Hiding in Plain Sight Two computer scientists found — in the unlikeliest of places — just the idea they needed to make a big leap in graph theory ...