* {{Cite book |author1=Biggs, Norman |author2=Lloyd, E. H. |author3=Wilson, Robin J. | title=Graph theory, 1736-1936 | date=1986 | publisher=Clarendon Press | location=Oxford [Oxfordshire] | isbn=0-19-853916-9 | pages=|title-link=Graph Theory, 1736–1936}} | * {{Cite book |author1=Biggs, Norman |author2=Lloyd, E. H. |author3=Wilson, Robin J. | title=Graph theory, 1736-1936 | date=1986 | publisher=Clarendon Press | location=Oxford [Oxfordshire] | isbn=0-19-853916-9 | pages=|title-link=Graph Theory, 1736–1936}} |