
Preprints
On graphs doublecritical with respect to the colouring number,
with A. S. Pedersen,
arXiv:1108.1036, submitted.
Vertexdisjoint directed and undirected cycles in general digraphs,
with J. BangJensen, A. Maddaloni, and S. Simonsen,
arXiv:1106.5885, submitted.
Nonseparating K_{4}subdivisions in graphs of minimum degree at least 4,
arXiv:1101.5278, submitted.
Large connected dominating matchings in K_{3}free K_{2,3}free graphs,
IMADA Preprint PP200906, submitted.
Tutte orientability, nowhere zero 3flows, and claw decompositions of squares and lexicographic products,
IMADA Preprint PP200815, submitted.
Orientations with prescribed outdegrees mod 3 of graphs where every edge is on some short cycles,
IMADA Preprint PP200814, submitted.
Degree Sequences and Edge Connectivity,
Preprint 282 at Hamburger Beiträge zur Mathematik, submitted.
Refereed Publications
The average degree of minimally contractioncritically 5connected graphs,
with K. Ando and Y. Egawa,
Journal of Graph Theory, published online.
DOI.
Axioms for infinite matroids,
with H. Bruhn, R. Diestel, R. Pendavingh, and P. Wollan,
Advances in Mathematics 239 (2013), 1846.
Minimal Connectivity, in
Topics in Structural Graph Theory,
edited by L. Beineke and R. Wilson,
Cambridge University Press (2012).
On the problem of finding disjoint cycles and dicycles in a digraph,
with J. BangJensen,
Combinatorica 31 (2011), 639668.
What is on his mind?,
with J. Barát,
Discrete Mathematics 310 (2010), 25732583.
DOI.
On Seymour's strengthening of Hadwiger's Conjecture for graphs with certain forbidden subgraphs,
Discrete Mathematics 310 (2010), 27142724.
DOI.
Balancing two spanning trees,
Networks 57 (2011), 351353.
DOI.
Packing Steiner trees on four terminals,
Journal of Combinatorial Theory (B) 100 (2010), 546553.
DOI.
Semantic Enhancement of Social Tagging Systems,
with F. Abel, N. Henze, and D. Krause,
Annals of Information Systems 6 (2009), 2554.
DOI.
Disjoint directed and undirected paths and cycles in digraphs,
with J. BangJensen,
Theoretical Computer Science 4649 (2009), 51385144.
DOI.
Edge disjoint Steiner trees in graphs without large bridges,
Journal of Graph Theory 62 (2009), 188198.
DOI.
Disjoint sub(di)graphs in digraphs,
with J. BangJensen,
European Conference on Combinatorics, Graph Theory and Applications (2009),
Electronic Notes in Discrete Mathematics 34 (2009), 179183.
DOI.
On the number of 4contractible edges in 4connected graphs,
with K. Ando, Y. Egawa, and K. Kawarabayashi,
Journal of Combinatorial Theory (B) 99 (2009), 97109.
DOI.
On the Effect of Group Structures on Ranking Strategies in Folksonomies,
with F. Abel, N. Henze, and D. Krause, in:
Weaving Services and People on the World Wide Web, Part 2,
Springer Berlin Heidelberg (2009), 275300.
DOI.
An elementary proof of Frank's characterization of the graphs having k edge disjoint spanning trees,
SUT Journal of Mathematics 44 (2008), 101107.
On the number of contractible triples in 3connected graphs,
Journal of Combinatorial Theory (B) 98 (2008), 136145.
DOI.
Vertex suppression in 3connected graphs,
Journal of Graph Theory 57 (2008), 4154.
DOI.
On small contractible subgraphs in 3connected graphs of small average degree,
Graphs and Combinatorics 23 (2007), 545557.
DOI.
A constructive characterization of the 3connected triangle free graphs,
Journal of Combinatorial Theory (B) 97 (2007), 358370.
DOI.
How to contract an essentially 6connected graph to a 5connected graph,
Discrete Mathematics 307 (2007), 494510.
DOI.
A generating theorem for 5regular simple planar graphs. I.,
with J. Kanno,
Congressus Numerantium 185 (2007), 127143.
There exist highly critically connected graphs of diameter 3,
Graphs and Combinatorics 22 (2006), 481485.
DOI.
Contractions, Cycle Double Covers, and Cyclic Colorings in Locally Connected Graphs,
Journal of Combinatorial Theory (B) 96 (2006), 881900.
DOI.
Mader's conjecture on extremely critical graphs,
Combinatorica 26 (2006), 277314.
DOI.
On the Pancyclicity of Lexicographic Products,
with T. Kaiser,
Graphs and Combinatorics 22 (2006), 5158.
DOI.
Average Degree and Contractibility,
Journal of Graph Theory 51 (2006), 205224.
DOI.
Global connectivity and expansion: long cycles and factors in fconnected graphs,
with S. Brandt, H. Broersma, and R. Diestel,
Combinatorica 26 (2006), 1736.
DOI.
Closed Separator Sets,
Combinatorica 25 (2005), 575598.
DOI.
A Pictured Memorandum on Synthesis Phenomena Occurring in the Homicidal Chauffeur Game,
with M. H. Breitner and A. Meyer,
Proceedings of the Fifth International ISDG Workshop,
International Society of Dynamic Games, Segovia (2005), 1732.
The Personal Publication Reader,
with F. Abel, R. Baumgartner, A. Brooks, C. Enzi, G. Gottlob,
N. Henze, M. Herzog, W. Nejdl, K. Tomaschewski,
Semantic Web Challenge, 4th International Semantic Web
Conference, Galway (2005).
Disjoint Apaths in Digraphs,
Journal of Combinatorial Theory (B) 95 (2005), 168172.
DOI.
Semantic Web enabled Information Systems: Personalized Views on Web Data,
with R. Baumgartner, C. Enzi, N. Henze, M. Herrlich, M. Herzog, K. Tomaschewski,
International Ubiquitous Web Systems and Intelligence Workshop, Singapore (UWSI 2005).
DOI.
Cayley DHTs  A GroupTheoretic Framework for Analyzing DHTs,
with W. Nejdl and C. Qu,
2nd International Symposium on Parallel and Distributed
Processing, Hongkong (ISPA 2004).
Also contained as a chapter in
Semantic Web and PeertoPeer,
S. Staab und H. Stuckenschmidt (eds.),
Springer Heidelberg (2005).
DOI.
Triangle Density and Contractibility,
Combinatorics, Probability and Computing 14 (2005), 133146.
DOI.
Personalization Functionality for the Semantic Web: Architectural Outline and First Sample Implementations,
with N. Henze,
1st International Workshop on Engineering the Adaptive Web (EAW 2004).
On decomposing a hypergraph into k connected subhypergraphs,
with A. Frank and T. Király,
Discrete Applied Mathematics 131 (2003), 373383.
DOI.
Edge disjoint trees containing some given vertices in a graph,
Journal of Combinatorial Theory (B) 88 (2003), 5365.
DOI.
A contribution to a conjecture of A. Saito,
Graphs and Combinatorics 18 (2002), 565571.
DOI.
A survey on contractible edges in graphs of a given vertex connectivity,
Graphs and Combinatorics 18 (2002), 130.
DOI.
Upper bounds to the number of vertices in a kcritically nconnected graph,
Graphs and Combinatorics 18 (2002), 133146.
DOI.
Almost all 3connected graphs contain a contractible set of k vertices,
Journal of Combinatorial Theory (B) 83 (2001), 305319.
DOI.
All 4connected line graphs of claw free graphs are Hamiltonian connected,
Journal of Combinatorial Theory (B) 82 (2001), 306315.
DOI.
On factors of 4connected claw free graphs,
with H. Broersma and Zd. Ryjácek,
Journal of Graph Theory 37 (2001), 125136.
DOI.
A degree sum condition for the existence of a contractible edge in a kconnected graph,
Journal of Combinatorial Theory (B) 82 (2001), 81101.
DOI.
Induced paths in 5connected graphs,
Journal of Graph Theory 36 (2001), 5258.
DOI.
The symmetric (2k,k)graphs,
Journal of Graph Theory 36 (2001), 3551.
DOI.
Contractible subgraphs in 3connected graphs,
Journal of Combinatorial Theory (B) 80 (2000), 3248.
DOI.
The kcritically 2kconnected graphs for k=3 and k=4,
Journal of Combinatorial Theory (B) 78 (2000), 6980.
DOI.
Contractible nonedges in triangle free graphs,
Graphs and Combinatorics 15 (1999), 429439.
On a conjecture of Thomassen and Toft,
Journal of Graph Theory 32 (1999), 118122.
Local spanning trees in graphs and hypergraph decomposition with respect to edge connectivity,
6th Twente Workshop on Graphs and Combinatorial Optimization (Enschede 1999),
Electron. Notes Discrete Math., 3, Elsevier, Amsterdam (1999).
DOI.
Edgedominating trails in ATfree graphs,
with E. Köhler,
6th Twente Workshop on Graphs and Combinatorial Optimization (Enschede 1999),
Electron. Notes Discrete Math., 3, Elsevier, Amsterdam (1999).
DOI.
Contractible nonedges in 3connected graphs,
Journal of Combinatorial Theory (B) 74 (1998), 192201.
DOI.
On kcritically connected line graphs,
Journal of Combinatorial Theory (B) 74 (1998), 17.
DOI.
Criticity Results Concerning the Connectivity of Graphs,
PhD Thesis, TU Berlin (1997).
A note on Hamiltonian Cycles
in Lexicographical Products,
Journal of Automata, Languages, and Combinatorics 2 (1997),
135138.
Editorial activities
 The Electronic Journal of Combinatorics
 Discrete Mathematics & Theoretical Computer Science
 AKCE International Journal of Graphs and Combinatorics
