@article{Groetschel1978, author = {Martin Gr{\"o}tschel}, title = {Hypo-Hamiltonian Facets of the Symmetric Travelling Salesman Polytope}, journal = {Zeitschrift f{\"u}r Angewandte Mathematik und Mechanik}, volume = {58}, pages = {T469 -- T471}, year = {1978}, }