DeNDeMA: Dependable Networks, Decomposition and Modular Algorithms
Project Topic
Modular algorithms in location theory, network design and routing
Project Description
Real-world complex systems (such as complex networks) usually exhibit
a modular structure and decompose into smaller units (subnetworks).
Moreover, one of the most fundamental tools in algorithm design is the
ability to build algorithms by composition. The goal of the project
is to exploit the modularity of modular networks/systems and to
develop concepts for the mathematical evaluation of composed
algorithms. A key issue in this context is the question, whether and
when a performance guarantee for all the modules does ensure a good
behavior of the whole (complex) system.
The aspect of modularization can be found in various scenarios, and it
is surprising that it has not been studied systematically yet.
Central issues of our project are the reduction of the complexity of
optimizations algorithms (both in terms of worst-case and average-case
complexity) and the error estimation of the tradeoff between greater
and smaller level of detail/aggregation of the solutions for the
single modules. The methods employed will be tools from multicriteria
optimization, game theory and online optimization.
Our project is divided into three major parts:
ModAlS: Modular Algorithms in Location Theory
Location theory suggest many possibilities for a modular approach,
e.g. aggregation of data, solving multi-facilities location problems
by exploiting information from single-facility problems, reduction of
center problems to covering problems, location on a tree as a modul of
general network location problems. To the best of our knowledge,
these possiblities have not been studied before.
There has been work on combining location problems mainly with routing
problems with the obvious application in industrial and econmical
design. New combinations with great potential are the integration of
scheduling/location (ScheLoc) or network flow/location (FlowLoc).
Surprisingly there has been no substantial work on these
combinations. Even if the single modules (location, scheduling,
network flow) are easy to solve (from a complexity point of view), the
integration may exhibit a new structure and give rise to new
mathematical methods.
In addition to the theoretical research we will study the impact on
application, e.g. in supply-chain management, logistics and the design
of distributed systems (see also project part
DisNDR).
We study modular algorithms in location theory and combinations of
location problems with other combinatorial optimization problems. The
goal is to develop theories which allow for an efficient solution of
mathematical location problems and a more realistic modelling of
real-world situations.
DisNDR: Distributed Network Design and Routing
The design of efficient networks and the routing within are both
classical fields of work in combinatorial optimization and computer
science. However, solutions for either problem require a global
insight on the network as a whole. In general, this assumption is not
met in the case of distributed networks, for once due to their dynamic
growth, and in most cases further due to the lack of central
authority. An example for this kind of network is a
Peer-to-Peer-Overlay Network: a heterogeneous cluster that is self
organizing and highly dynamic.
An important characterization of distributed networks is that they
consist of multiple processes running only in parts, e.g. certain
vertices, of the network. Furthermore, these processes may have bad
coordination, as well as slow, expensive and unreliable communication
channels. These properties distinguish a distributed network from the
usual network commonly used in combinatorial optimization.
The project deals with two basic aspects of distributed networking:
design and communication (routing). Both fields long for efficient,
distributed combinatorial algorithms, to be designed and
analyzed. They must meet certain requirements. The key-issue is if and
how performance guarantees for the several modules can be conferred to
the system. These algorithms serve as a layout for the design of
reliable distributed system, based on Peer-to-Peer approaches for
example.
A vision is to develop an applicable theory for evaluating algorithms
in modular systems. Such systems are found in the fields of
supply-chain-management, location theory (see
e.g.
ModAlS), traffic planning (see
e.g.
GamDR) and many more.
The main focus of our work lies in the application on distributed
systems, with emphasis on the design and analysis of
Peer-to-Peer-Overlays.
GamDR: Game Theoretic Aspects of Distributed Network
Distributed competitive decision making, as opposed to centralized
planning, is emerging as the norm in many systems. A prime example is
the Internet which is mainly a large collection of independently
administered autonomous entities who typically take unilateral
decisions, such as selecting a path to route their packets, in order
to maximize their own utility. It is well known that self-interest
can deplete a common resource. It seems this also applies to the
Internet and other networks, which are slowed by those who hurry the
most.
The issue of selfish routing has received a lot of attention in the
recent years, from both the theory as well as the networking
communities. Fostered by the desire to advance the understanding of
the technological and sociological properties of the Internet, ideas
from algorithmic computer science and game theory have been used to
study the behavior of networks under distributed decision processes.
Most networks decompose into modules and it is often the case that
these sub-networks are controlled by selfish agencies. The selfish
users which use the modular network can be viewed as a very fine
grained modularization.
The first goal of the project is to develop new methods, to evaluate
the qualilty of complex distributed/modular networks which are used by
selfish users. In a second step we will construct and analyse methods
to design and control such networks.
Project Members
Project Chair
Participating Research Groups
- Optimization Group (Department of Mathematics)
- Distributed Algorithms Group (Department of Computer Science)
- Sect. Optimization (Fraunhofer Institute for Industrial Mathematics (ITWM))
- Technomathematics Group (Department of Mathematics)
Scientific Personnel
- Thomas Fischer
- Katharina Gerhardt, geb. Rupp
- Cigdem Güler
- Sleman Saliba
- Heike Sperber
- Akin Tanatmis
- Stephan Westphal
- Steffen Wolf
External Cooperation
- Optimization Group, Distributed Algorithms Group and Sect. Optimization: cooperation with project SupChain
- Technomathematics Group: cooperation with project NetSim
- Andreas Ernst, CSIRO, Melbourne, Australia
- Richard Francis, University of Florida, USA
- Frank Plastria, Vreije Universiteit Brussel, Belgium
- Justo Puerto, Universidad de Sevilla, Spain
- Vedat Verter, McGill University, Canada
- Madhav V. Marathe, Virginia Bioinformatics Institute, USA
- Aravind Srinivasan, Dept. of Computer Science, University of Maryland, USA
- S. S. Ravi, Dept. of Computer Science, State University of New York at Albany, USA
- Riko Jacob, ETH Zürich, Switzerland
- Elisabeth Gassner, Technical University Graz, Austria
- Johannes Hatzl, Technical University Graz, Austria
Project Events and Achievements
- Project start: October 1st, 2005
- Project end: December 31st, 2007
Events
Presentations
- H. Sperber: How hard is it to find extreme Nash equilibria in network congestion games?, Workshop on Internet and Network Economics (WINE 2008), Shanghai, China, December 2008
- H. Hamacher: Source Location Problems, Technische Universität Graz, Dezember 2008
- H. Hamacher: Optimierungsmodelle in der Planung von Evakuierung und Krebsbestrahlung, Universität Graz, Dezember 2008
- H. Hamacher: Simultaneous intensity and realization optimization in radiation therapy, Huangguoshu International Interdisciplinary Conference on Biomedical Mathematics, China, November 2008
- H. Hamacher: Multiple criteria optimization in location theory, Multi Criteria Decision Analysis 68, Kreta, October 2008
- M. Kalsch: Simultaneous Scheduling and Location (ScheLoc), EURO Working Group on Locational Analysis, EWGLA XVII, Elche/Alicante, Spain, September 2008
- A. Tanatmis: A Separation Algorithm for Improved Linear Programming-Decoding of Linear Block Codes, 12. Workshop Future Research in Combinatorial Optimization, Heidelberg, Germany, September 2008
- M. Kalsch: How to solve Scheduling and Location Problems - Simultaneously?, 12. Workshop Future Research in Combinatorial Optimization, Heidelberg, Germany, September 2008
- A. Tanatmis and S. Ruzika: A Separation Algorithm for Improved Linear Programming-Decoding of Linear Block Codes, 5th International Symposium on Turbo Codes & Related Topics, Lausanne, Switzerland, September 2008
- S. O. Krumke: Operations Research as a decision support tool in society, Euroscience Open Forum, Barcelona, July 2008
- D. P. Gross and H. Hamacher: Multiobjective Source Location Problems, International Symposium on Locational Decisions (ISOLDE), Santa Barbara, California, USA, Juli 2008
- M. Kalsch and H. Hamacher: Simultaneous Scheduling and Location, International Symposium on Locational Decisions (ISOLDE), Santa Barbara, California, USA, Juli 2008
- C. Güler: Inverse Tension Problems, Cologne Twente Workshop on Graphs and Combinatorial Optimization, May 2008, Gargnano, Italy
- S. Ruzika: Schnelle Algorithmen für verallgemeinerte Flaschenhalsprobleme bei der Registrierung biometrischer Daten, Südwest-Workshop Optimierung, Darmstadt, February 2008
- S. O. Krumke: Stark polynomiale Algorithmen für budget-restringierte Maximalflussprobleme, Südwest-Workshop Optimierung, Darmstadt, February 2008
- H. Hamacher: Location theory plus x: FlowLoc and ScheLoc, University of Auckland, February 2008
- S. O. Krumke: Online Optimiziation: Continuously discrete or discretely continuous, SIGOPT - International Conference on Optimization, Lambrecht, February 2008
- C. Güler: Capacity Inverse Minimum Cost Flows, ORP3 2007 Conference, September 2007, Guimaraes, Portugal
- M. Kalsch: Scheduling and Location (ScheLoc): Makespan Problem with Variable Release Dates, 3rd Multidisciplinary International Conference on Scheduling: Theory and Applications, MISTA 2007, Paris, France, August 2007
- K. Gerhardt: A Distributed Algorithm for Constructing Sparsest 2-edge Connected Spanning Subgraphs, LOCALITY 2007, Portland/Oregon, USA, August 2007
- K. Gerhardt: Stochastic Scheduling with Application to Vehicle Routing, 8th workshop on Models and Algorithms for Planning and Scheduling Algorithms, Istanbul, Turkey, July 2007
- C. Güler: Capacity Inverse Minimum Cost Flows, 22nd European Conference on Operational Research EURO XXII, July 2007, Prague, Czech Republic
- D.R. Poetranto: Minimum Cost Single-cover Source Location Problem on Undirected Networks, The 5th Hungarian-Japanese Symposium on Discrete Mathematics and Its Applications, Sendai, Japan, April 2007
- M. Kalsch: Integrated Scheduling and Location Models (ScheLoc), Sitzung der GOR-AG Projektmanagement und Scheduling, INFORM GmbH, Aachen, Germany, April 2007
- D.R. Poetranto: Location Problem to Satisfy Unsplittable Demand on Undirected Capacitated Networks, EWGLA XVI Meeting, Estoril, Portugal, February 2007
- T. Meyer: The Absolute p-Hub Center Problem, EWGLA XVI Meeting, Estoril, Portugal, February 2007
- M. Kalsch: Planar Scheduling Location Problems, EWGLA XVI Meeting, Estoril, Portugal, February 2007
- D.R. Poetranto: A General Model of Location Problems on Capacitated Networks, EURO Winter Institute on Location and Logistics 2007, Estoril, Portugal, January 2007
- D.R. Poetranto: Stop Location Design in Public Transportation Networks: An Idea for New Public Transportation Systems in Indonesia, International Conference on Mathematics and Natural Sciences (ICMNS) 2006, Bandung, Indonesia, November 2006
- H. Sperber: On Nash Flows in Series-Parallel Graphs, Workshop on Network Optimization, Lambrecht, October 2006
- S. Saliba: Approximation Algorithms for a Real World Vehicle Dispatching Problem, Operations Research 2006, Karlsruhe, September 2006
- D.R. Poetranto: Source Location Problem on A Tree Network, Workshop on Network Optimization, Lambrecht, October 2006
- T. Meyer: Hub location with process times and its potential in the postal distribution network, Operations Research 2006, Karlsruhe, September 2006
- M. Kalsch: Scheduling Location Problems, Operations Research 2006, Karlsruhe, September 2006
- S. Saliba: Approximation Algorithms for a Vehicle Dispatching Problem, EURO Summer Institute 2006 Optimization Challanges in Engineering: Methods, Software and Applications, Lutherstadt Wittenberg, August 2006
- S.O. Krumke: Algorithms for Routing, Traffic Colloqium Dresden, July 2006
- S. Westphal: Competitive Algorithms for Cottage Rental, Cologne-Twente-Workshop on Graphs and Combinatorial Optimization, Lambrecht, June 2006
- S. Saliba: Approximation Algorithms for Routing, Cologne-Twente-Workshop on Graphs and Combinatorial Optimization, Lambrecht, June 2006
- S.O. Krumke: Online Optimization in Transport and Logistics, Kolloqium WU Wien, June 2006
- D.R. Poetranto: FlowLoc: The Source-Location Problem, ECCO XIX - CO2006 Joint Meeting, Porto, Portugal, May 2006
- M. Kalsch: Universal Scheduling Problems, ECCO XIX - CO2006 Joint Meeting, Porto, Portugal, May 2006
- S.O. Krumke: What's next? The challenge of online optimization, Invited Plenary Vortrag COFIN/Matheon Workshop, Menaggio, Italy, May 2006
- S.O. Krumke: On Minimizing the Maximum Flow Time in the Online Dial-a-Ride Problem, 3rd Workshop on Approximation and Online Algorithms, Palma de Mallorca, October 2005
- S.O. Krumke: Deterministic Online Optical Call Admission Revisited, 3rd Workshop on Approximation and Online Algorithms, Palma de Mallorca, October 2005
Project Publications
Jochen Gorski, Stefan Ruzika. In:
Operations Research Letters. 2009
Davaatseren Baatar, Natashia Boland, Robert Johnston, Horst W. Hamacher. In:
INFORMS Journal on Computing. 2009
Anne M. Schwahn. Technical Report, Report in Wirtschaftsmathematik, TU Kaiserslautern, December, 2008
Elisabeth Gassner, Johannes Hatzl, Sven O. Krumke, Heike Sperber, Gerhard J. Woeginger. In: Christos Papadimitriou and Shuzhong Zhang ed.,
The 4th International Workshop On Internet And Network Economics (WINE 2008) , Shanghai, China. LNCS, Volume 5385, Springer, P. 82-93, December, 2008
Heike Sperber. Technical Report, Report in Wirtschaftsmathematik, Volume 116, TU Kaiserslautern, November, 2008
Clemens Thielen. Submitted, October, 2008
Clemens Thielen, Sven O. Krumke. In:
6th Workshop on Approximation and Online Algorithms, WAOA 2008 , Karlsruhe, Germany. LNCS, Volume 5426, Springer, P. 105- -118, September, 2008
Matthias Ehrgott, Cigdem Güler, Horst W. Hamacher, Lizhen Shao. In:
A Quarterly Journal of Operations Research: 4OR. Volume 6, P. 199--262, September, 2008
Clemens Thielen. Submitted, August, 2008
Cigdem Güler. Technical Report, Number 114, Tu Kaiserslautern, July, 2008
Kerstin Bauer, Thomas Fischer, Sven O. Krumke, Katharina Gerhardt nee Rupp, Stephan Westphal, Peter Merz. In:
Proceedings of EvoCOP 2008 - Eigth European Conference on Evolutionary Computation in Combinatorial Optimisation. Lecture Notes in Computer Science, 2008
Sameh Al-Shihabi, Peter Merz, Steffen Wolf. In:
LION~II: Learning and Intelligent OptimizatioN Conference. LNCS, Won a Best Paper Award. Post-Proceedings still to be published, 2008
Dwi Retnani Poetranto, Horst W. Hamacher, Simone Horn, Anita Schöbel. In:
TOP (Journal der Spanischen OR Gesellschaft), Online First. 2008
Marcel Kalsch, Zvi Drezner. Submitted, 2008
Inka Kaufmann, Marcel Kalsch, Tanja Meyer. In:
Proceedings of the 4th IWA Young Water Professionals Conference. University of California, Berkeley, USA, 2008
Sven O. Krumke, Dirk Räbiger, Rainer Schrader. In:
Discrete Applied Mathematics. Volume 156, Number 17, P. 3298- -3304, 2008
Sven O. Krumke, Anne M. Schwahn, Rob van Stee, Stephan Westphal. In:
Operations Research Letters. Volume 36, Number 2, P. 247- -249, 2008
Matthias Altenhoefer, Riko Jacob, Sven O. Krumke. Submitted, 2008
Cigdem Güler, Horst W. Hamacher. In:
Journal of Combinatorial Optimization, Online First. 2008
Donatas Elvikis, Horst W. Hamacher, Marcel Kalsch. In:
Journal of Scheduling, Online First. 2008
Horst W. Hamacher, Frank Kienle, Mayur Punekar, Stefan Ruzika, Akin Tanatmis, Norbert Wehn. In:
Proceedings of the 5th International Symposium on Turbo Codes 2008 & Related Topics. 2008
Donatas Elvikis, Horst W. Hamacher, Marcel Kalsch. In:
3rd Multidisciplinary International Conference on Scheduling: Theory and Applications, MISTA 2007. P. 152--158, August, 2007
Alexander J. Perez Tchernov, Anne M. Schwahn. Technical Report, Reports in Wirtschaftsmathematik, Number 112, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2007/2118/, July, 2007
Katharina Gerhardt nee Rupp, Sven O. Krumke. In: _Eight Workshop on Models and Algorithms for Planning and Scheduling Problems (MAPSP 2007) _. July, 2007
Silke Jütte, Elena Gavriliouk, Horst W. Hamacher. Technical Report, Reports in Wirtschaftsmathematik, Number 109, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2007/2088/, April, 2007
Holger Hennes, Horst W. Hamacher. In:
Studies in Locational Analysis. Number 16, P. 77--90, March, 2007
Donatas Elvikis, Horst W. Hamacher, Marcel Kalsch. Technical Report, Reports in Wirtschaftsmathematik, Number 106, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2007/2062/, Februrary, 2007
Horst W. Hamacher, Christian R. Pedersen, Stefan Ruzika. In:
European Journal of Operational Research. Volume 176, P. 1404--1422, 2007
Inka Kaufmann, Tanja Meyer, Marcel Kalsch, Theo G. Schmitt, Horst W. Hamacher. In:
Advanced Sanitation 2007, Aachen, Germany. 2007
Inka Kaufmann, Theo G. Schmitt, Tanja Meyer, Marcel Kalsch, Horst W. Hamacher. In:
NOVATECH 2007, The 6th international conference on sustainable techniques and strategies in urban water management, Lyon, France. 2007
Dwi Retnani Poetranto. In:
Euro Winter Institute on Location and Logistics, Estoril, Portugal. P. 333--347, 2007
Florentine Bunke, Horst W. Hamacher, Francesco Maffioli, Anne M. Schwahn. Technical Report, Reports in Wirtschaftsmathematik, Number 108, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2007/2087/, 2007
Steffen Wolf. Technical Report, Number 363/07, University of Kaiserslautern, 2007
Steffen Wolf, Peter Merz. In: Thomas Bartz-Beielstein and others ed.,
Hybrid Metaheuristics, Proceedings. LNCS, Volume 4771, Springer, P. 1--15, 2007
Tim Nonner, Sven O. Krumke, Peter Merz, Katharina Gerhardt nee Rupp. In:
Proc. 11th International Conference on Principles of Distributed Systems (OPODIS). LNCS, Submitted, 2007
Thomas Fischer. In:
MIC'2007 -- 7th Metaheuristics International Conference}. 2007
Thomas Fischer, Peter Merz. In: Bartz-Beielstein and Aguilera and Blum and Naujoks and Roli and Rudolph and Sampels ed.,
HM 2007 -- 4th International Workshop on Hybrid Metaheuristics. LNCS, Volume 4771, Springer, P. 170--184, 2007
Peter Merz, Steffen Wolf. In: Torsten Braun and Georg Carle and Burkhard Stiller ed.,
KiVS 2007: Kommunikation in Verteilten Systemen -- Workshops. VDE-Verlag, P. 231--242, 2007
Stefan Ruzika. Technische Universität Kaiserslautern, 2007
Stephan Westphal, Sven O. Krumke, Rob van Stee. In: S. S. Ravi and S. K. Shukla ed.,
Fundamental Problems in Computing: Essays in Honor of Professor Daniel J. Rosenkrantz. Springer, 2007
Cigdem Güler, Horst W. Hamacher. In:
The Forth Edition of ORP3 (Operational Research Peripatetic Post-Graduate Programme). 2007
Maurizio Bruglieri, Matthias Ehrgott, Horst W. Hamacher, Francesco Maffioli. In:
Discrete Applied Mathematics. Volume 154, P. 1344--1357, 2006
Sleman Saliba. In:
Central European Journal of Operationd Research. Volume 14, P. 313--336, 2006
Alexander Engau, Horst W. Hamacher. In:
Networks. Available at
http://kluedo.ub.uni-kl.de/volltexte/2006/1971/, Submitted, 2006
Jochen Gorski, Kathrin Klamroth, Stefan Ruzika. In:
Operations Research. Available at
http://kluedo.ub.uni-kl.de/volltexte/2006/2039/, Submitted, 2006
Horst W. Hamacher, Tanja Meyer. Technical Report, Reports in Wirtschaftsmathematik, Number 98, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2006/1966/, 2006
Horst W. Hamacher, Stefan Ruzika, Stevanus A. Tjandra. In:
Discrete Optimization. Volume 3 , P. 238--254, 2006
Stephan Westphal, Sven O. Krumke. In:
Annals of Operations Research. To Appear, available at
ftp://www.mathematik.uni-kl.de/pub/scripts/krumke/mista05.pdf, 2006
Matthias Ehrgott, Horst W. Hamacher, Marc Nußbaum. Technical Report, Reports in Wirtschaftsmathematik, Number 101, Technische Universität Kaiserslautern, Available at
http://kluedo.ub.uni-kl.de/volltexte/2006/2033/, 2006
Inka Kaufmann, Marcel Kalsch, Tanja Meyer, Horst W. Hamacher, Theo G. Schmitt. In:
siwawi 2030- Themen und Lösungsansätze für die nächsten 25 Jahre. Number 25, Technische Universität Kaiserslautern, FG Siedlungswasserwirtschaft, P. 211--247, 2006
Anita Schöbel, Horst W. Hamacher, Annegret Liebers, Dorothea Wagner. In:
Asia Pacific Journal of Operations Research. Submitted, 2006
Horst W. Hamacher, Stefan Ruzika, Akin Tanatmis. In:
Operations Research Spectrum. Available at
http://kluedo.ub.uni-kl.de/volltexte/2006/2021/, Submitted, 2006
Benjamin Hiller, Sven O. Krumke, Jörg Rambau. In:
Discrete Applied Mathematics. To Appear, 2006
Amin Coja-Oghlan, Sven O. Krumke, Till Nierhoff. In:
Journal of Algorithms. Volume 61, P. 1--19, 2006
Sven O. Krumke, Sleman Saliba, Tjark Vredeveld, Stephan Westphal. In:
International Conference on Operations Research. 2006
Peter Merz, Steffen Wolf. In: Thomas Philip Runarsson and Hans-Georg Beyer and Edmund Burke and Juan J. Merelo-Guerv{\'o}s and L. Darrell Whitley and Xin Yao ed.,
Proceedings of the 9th International Conference on Parallel Problem Solving from Nature - PPSN IX. LNCS, Volume 4193, Springer, P. 272--281, 2006
Peter Merz. In:
Workshop on Performance Modeling of Self-Organizing Systems (IWSOS). University of Passau, 2006
Sandra Gutierrez, Sven O. Krumke, Nicole Megow, Tjark Vredeveld. In:
Theoretical Computer Science. Volume 361, Number 2, P. 329 - 341, 2006
Horst W. Hamacher, Christian R. Pedersen, Stefan Ruzika. In:
Operations Research Letters. To Appear, 2005
Sven O. Krumke, Hartmut Noltemeier. B.G.Teubner, ISBN 3-519-00526-3, 2005
Sven O. Krumke, Willem E. de Paepe, Diana Poensgen, Maarten Lipmann, Alberto Marchetti-Spaccamela. In:
The 3rd Workshop on on Approximation and Online Algorithms. Lecture Notes in Computer Science, Volume 3879, Springer, P. 258--269, 2005
Stefan Heinz, Sven O. Krumke, Nicole Megow, Jörg Rambau, Andreas Tuchscherer. In:
The 3rd Workshop on on Approximation and Online Algorithms. Lecture Notes in Computer Science, Volume 3879, Springer, P. 230--243, 2005
Ravindra K. Ahuja, Horst W. Hamacher. In:
Networks. Volume 45, P. 36--41, 2005
Davaatseren Baatar, Matthias Ehrgott, Horst W. Hamacher, Gerhard J. Woeginger. In:
Discrete Applied Mathematics. Volume 152, P. 6--34, 2005
Amin Coja-Oghlan, Sven O. Krumke, Till Nierhoff. In:
Journal of Scheduling. Volume 8, P. 197--210, 2005
Elisabeth Gassner, Sven O. Krumke. In:
The 3rd Workshop on on Approximation and Online Algorithms. Lecture Notes in Computer Science, Volume 3879, Springer, P. 190--202, 2005
Matthias Ehrgott, Stefan Ruzika. Technical Report, Reports in Wirtschaftsmathematik, Number 96, Available at
http://kluedo.ub.uni-kl.de/volltexte/2005/1893/, 2005
Dwi Retnani Poetranto. In:
The 3rd ORP3 Meeting, Valencia, Spain. P. 297--310, 2005
