@inproceedings{GroetschelPadberg1978, author = {Martin Gr{\"o}tschel and Manfred Padberg}, title = {On the symmetric travelling salesman problem}, booktitle = {Optimization and operations research, Proc. Workshop, Bonn 1977}, editor = {Rudolf Henn and Bernhard Korte and W. Oettli}, volume = {157}, pages = {105 -- 115}, year = {1978}, }