Counterexamples to three conjectures concerning perfect graphs. - Stefan Hougardy (Discret. Math., 1993)

Probabilistically checkable proofs and their consequences for approximation algorithms. - Stefan Hougardy; Hans Jürgen Prömel; Angelika Steger (Discret. Math., 1994)

Even and odd pairs in linegraphs of bipartite graphs. - Stefan Hougardy (Eur. J. Comb., 1995)

Even pairs and the strong perfect graph conjecture. - Stefan Hougardy (Discret. Math., 1996)

On the P4-Structure of Perfect Graphs V. Overlap Graphs. - Chính T. Hoàng; Stefan Hougardy; Frédéric Maffray (J. Comb. Theory B, 1996)

Proof Checking and Non-approximability. - Stefan Hougardy (Lectures on Proof Verification and Approximation Algorithms, 1997)

Perfect graphs with unique P4-structure. - Stefan Hougardy (Discret. Math., 1997)

Does the Jones Polynomial Detect Unknottedness? - Oliver T. Dasbach; Stefan Hougardy (Exp. Math., 1997)

Wing-triangulated graphs are perfect. - Stefan Hougardy; Van Bang Le; Annegret Wagler (J. Graph Theory, 1997)

Uniquely Colourable Graphs and the Hardness of Colouring Graphs of Large Girth. - Thomas Emden-Weinert; Stefan Hougardy; Bernd Kreuter (Comb. Probab. Comput., 1998)

A 1.598 Approximation Algorithm for the Steiner Problem in Graphs. - Stefan Hougardy; Hans Jürgen Prömel (SODA, 1999)

On wing-perfect graphs. - Stefan Hougardy (J. Graph Theory, 1999)

Lower Bounds for Approximation Algorithms for the Steiner Tree Problem. - Clemens Gröpl; Stefan Hougardy; Till Nierhoff; Hans Jürgen Prömel (WG, 2001)

Polynomial time recognition of P4-structure. - Ryan B. Hayward; Stefan Hougardy; Bruce A. Reed (SODA, 2002)

Steiner trees in uniformly quasi-bipartite graphs. - Clemens Gröpl; Stefan Hougardy; Till Nierhoff; Hans Jürgen Prömel (Inf. Process. Lett., 2002)

Recursive generation of partitionable graphs. - Endre Boros; Vladimir Gurvich; Stefan Hougardy (J. Graph Theory, 2002)

Improved Linear Time Approximation Algorithms for Weighted Matchings. - Doratha E. Drake; Stefan Hougardy (RANDOM-APPROX, 2003)

Linear Time Local Improvements for Weighted Matchings in Graphs. - Doratha E. Drake; Stefan Hougardy (WEA, 2003)

Accelerating screening of 3D protein data with a graph theoretical approach. - Cornelius Frömmel; Christoph Gille; Andrean Goede; Clemens Gröpl; Stefan Hougardy; Till Nierhoff; Robert Preissner; Martin Thimm (Bioinform., 2003)

A simple approximation algorithm for the weighted matching problem. - Doratha E. Drake; Stefan Hougardy (Inf. Process. Lett., 2003)

On simplicial and co-simplicial vertices in graphs. - Chính T. Hoàng; Stefan Hougardy; Frédéric Maffray; Nadimpalli V. R. Mahadev (Discret. Appl. Math., 2004)

On approximation algorithms for the terminal Steiner tree problem. - Doratha E. Drake; Stefan Hougardy (Inf. Process. Lett., 2004)

Comparison of 2D Similarity and 3D Superposition. Application to Searching a Conformational Drug Database. - Martin Thimm; Andrean Goede; Stefan Hougardy; Robert Preissner (J. Chem. Inf. Model., 2004)

Perfectness is an Elusive Graph Property. - Stefan Hougardy; Annegret Wagler (SIAM J. Comput., 2004)

A linear-time approximation algorithm for weighted matchings in graphs. - Doratha E. Drake Vinkemeier; Stefan Hougardy (ACM Trans. Algorithms, 2005)

Classes of perfect graphs. - Stefan Hougardy (Discret. Math., 2006)

On a conjecture of Hoàng and Tu concerning perfectly orderable graphs. - Stefan Hougardy (Discret. Math., 2006)

Approximating weighted matchings in parallel. - Stefan Hougardy; Doratha E. Drake Vinkemeier (Inf. Process. Lett., 2006)

Lower bounds for the relative greedy algorithm for approximating Steiner trees. - Stefan Hougardy; Stefan Kirchner (Networks, 2006)

Computation of best possible low degree expanders. - Stefan Hougardy; Ivo Köthnig (Discret. Appl. Math., 2007)

Linear Time Approximation Algorithms for Degree Constrained Subgraph Problems. - Stefan Hougardy (Bonn Workshop of Combinatorial Optimization, 2008)

Surface Realization with the Intersection Segment Functional. - Stefan Hougardy; Frank H. Lutz; Mariano Zelke (Exp. Math., 2010)

The Floyd-Warshall algorithm on graphs with negative cycles. - Stefan Hougardy (Inf. Process. Lett., 2010)

On packing squares into a rectangle. - Stefan Hougardy (Comput. Geom., 2011)

BonnCell: Automatic layout of leaf cells. - Stefan Hougardy; Tim Nieberg; Jan Schneider 002 (ASP-DAC, 2013)

Edge Elimination in TSP Instances. - Stefan Hougardy; Rasmus T. Schroeder (WG, 2014)

On the integrality ratio of the subtour LP for Euclidean TSP. - Stefan Hougardy (Oper. Res. Lett., 2014)

On the nearest neighbor rule for the metric traveling salesman problem. - Stefan Hougardy; Mirko Wilde (Discret. Appl. Math., 2015)

The approximation ratio of the greedy algorithm for the metric traveling salesman problem. - Judith Brecklinghaus; Stefan Hougardy (Oper. Res. Lett., 2015)

An exact algorithm for wirelength optimal placements in VLSI design. - Julia Funke; Stefan Hougardy; Jan Schneider 002 (Integr., 2016)

Automatic Cell Layout in the 7nm Era. - Pascal Cremer; Stefan Hougardy; Jan Schneider 002; Jannik Silvanus (ISPD, 2017)

Dijkstra meets Steiner: a fast exact goal-oriented Steiner tree algorithm. - Stefan Hougardy; Jannik Silvanus; Jens Vygen (Math. Program. Comput., 2017)

The approximation ratio of the 2-Opt Heuristic for the metric Traveling Salesman Problem. - Stefan Hougardy; Fabian Zaiser; Xianghui Zhong (Oper. Res. Lett., 2020)

BonnCell: Automatic Cell Layout in the 7-nm Era. - Pascal Van Cleeff; Stefan Hougardy; Jannik Silvanus; Tobias Werner 001 (IEEE Trans. Comput. Aided Des. Integr. Circuits Syst., 2020)

The Approximation Ratio of the 2-Opt Heuristic for the Euclidean Traveling Salesman Problem. - Ulrich A. Brodowsky; Stefan Hougardy (STACS, 2021)

The Approximation Ratio of the k-Opt Heuristic for the Euclidean Traveling Salesman Problem. - Ulrich A. Brodowsky; Stefan Hougardy; Xianghui Zhong (CoRR, 2021)

Hard to solve instances of the Euclidean Traveling Salesman Problem. - Stefan Hougardy; Xianghui Zhong (Math. Program. Comput., 2021)

The Approximation Ratio of the k-Opt Heuristic for the Euclidean Traveling Salesman Problem. - Ulrich A. Brodowsky; Stefan Hougardy; Xianghui Zhong (SIAM J. Comput., 2023)

A Fast Optimal Double-row Legalization Algorithm. - Stefan Hougardy; Meike Neuwohner; Ulrike Schorr (ACM Trans. Design Autom. Electr. Syst., 2023)

The k-Opt Algorithm for the Traveling Salesman Problem Has Exponential Running Time for k ≥ 5. - Sophia Heimann; Hung P. Hoang 001; Stefan Hougardy (ICALP, 2024)

The Bottom-Left Algorithm for the Strip Packing Problem. - Stefan Hougardy; Bart Zondervan (IWOCA, 2024)

Fast Approximation Algorithms for Euclidean Minimum Weight Perfect Matching. - Stefan Hougardy; Karolina Tammemaa (WAOA, 2024)

Local elimination in the traveling salesman problem. - William J. Cook; Keld Helsgaun; Stefan Hougardy; Rasmus T. Schroeder (Math. Program. Comput., 2024)

37.1 IBM Telum II Processor Design-Technology Co-Optimizations for Power, Performance, Area, and Reliability. - David Wolpert 001; Gerry Strevig; Christopher J. Berry; Leon J. Sigal; Bill Huott; Mark Cichanowski; Matthias Pflanz; Tobias Werner 001; Philipp Salz; Nick Jinq; Michael Romain; Iris Leefken; et al. (ISSCC, 2025)

A near-complete resolution of the exponential-time complexity of k-opt for the traveling salesman problem. - Sophia Heimann; Hung P. Hoang 001; Stefan Hougardy (CoRR, 2025)