Strong and weak edges of a graph and linkages with the vertex cover problem

In this paper we show that the problem of identifying an edge ( i , j ) of a graph G such that there exists an optimal vertex cover S of G containing exactly one of the vertices i and j is NP-hard. Such an edge is called a weak edge. We then develop a polynomial time approximation algorithm for the...

Full description

Saved in:
Bibliographic Details
Published inDiscrete Applied Mathematics Vol. 160; no. 3; pp. 197 - 203
Main Authors Han, Qiaoming, Punnen, Abraham P.
Format Journal Article
LanguageEnglish
Published Kidlington Elsevier B.V 01.02.2012
Elsevier
Subjects
Online AccessGet full text

Cover

Loading…
Abstract In this paper we show that the problem of identifying an edge ( i , j ) of a graph G such that there exists an optimal vertex cover S of G containing exactly one of the vertices i and j is NP-hard. Such an edge is called a weak edge. We then develop a polynomial time approximation algorithm for the vertex cover problem with performance guarantee 2 − 1 1 + σ , where σ is an upper bound on a measure related to a weak edge of a graph. A related problem of identifying an edge ( i , j ) such that there exists an optimal vertex cover containing both vertices i and j is also shown to be NP-hard. Further, we discuss a new relaxation of the vertex cover problem which is used in our approximation algorithm to obtain smaller values of σ . We also obtain linear programming representations of the vertex cover problem on special graphs.
AbstractList In this paper we show that the problem of identifying an edge (i,j) of a graph G such that there exists an optimal vertex cover S of G containing exactly one of the vertices i and j is NP-hard. Such an edge is called a weak edge. We then develop a polynomial time approximation algorithm for the vertex cover problem with performance guarantee [inline image], where sigma is an upper bound on a measure related to a weak edge of a graph. A related problem of identifying an edge (i,j) such that there exists an optimal vertex cover containing both vertices i and j is also shown to be NP-hard. Further, we discuss a new relaxation of the vertex cover problem which is used in our approximation algorithm to obtain smaller values of sigma . We also obtain linear programming representations of the vertex cover problem on special graphs.
In this paper we show that the problem of identifying an edge ( i , j ) of a graph G such that there exists an optimal vertex cover S of G containing exactly one of the vertices i and j is NP-hard. Such an edge is called a weak edge. We then develop a polynomial time approximation algorithm for the vertex cover problem with performance guarantee 2 − 1 1 + σ , where σ is an upper bound on a measure related to a weak edge of a graph. A related problem of identifying an edge ( i , j ) such that there exists an optimal vertex cover containing both vertices i and j is also shown to be NP-hard. Further, we discuss a new relaxation of the vertex cover problem which is used in our approximation algorithm to obtain smaller values of σ . We also obtain linear programming representations of the vertex cover problem on special graphs.
Author Punnen, Abraham P.
Han, Qiaoming
Author_xml – sequence: 1
  givenname: Qiaoming
  surname: Han
  fullname: Han, Qiaoming
  email: qmhan@zufe.edu.cn
  organization: School of Mathematics and Statistics, Zhejiang University of Finance and Economics, Hangzhou, Zhejiang 310018, PR China
– sequence: 2
  givenname: Abraham P.
  surname: Punnen
  fullname: Punnen, Abraham P.
  email: apunnen@sfu.ca
  organization: Department of Mathematics, Simon Fraser University, 13450 102nd Ave., Surrey, BC V3T5X3, Canada
BackLink http://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=25335349$$DView record in Pascal Francis
BookMark eNp9kDtPwzAQxy0EEm3hA7B5QWJJ8Dlx4ogJVbxEJQZAYosc59K6zaPYaQvfHodWjCz3_N2d7j8mx23XIiEXwEJgkFwvw1I1IWcAPg8ZT4_ICGTKgyRN4ZiMPJMEHOTHKRk7t2SMgc9G5Pm1t107p6ot6Q7VimI5R0e7iio6t2q9-O3Upl2pob4z_YL2C6RbtD1-Ud35gK5tV9TYnJGTStUOzw9-Qt7v796mj8Hs5eFpejsLdMyiPoh5WsQsQ6wgk0LzUmSJQFCRZglPRemtlixhqYIYZYEAKq3iSAqRQSFRRBNytd_r735u0PV5Y5zGulYtdhuXe0FYBhJi6VHYo9p2zlms8rU1jbLfHhq4JF_mXrh8EG4oeeH8zOVhvXJa1ZVVrTbub5CLKBJRnHnuZs-h_3Vr0OZOG2w1lsai7vOyM_9c-QGwboLB
CODEN DAMADU
CitedBy_id crossref_primary_10_1109_ACCESS_2019_2918028
Cites_doi 10.1145/1597036.1597045
10.1007/BF01580222
10.1137/S0895480195287541
10.4086/toc.2006.v002a002
10.1016/j.orl.2009.01.010
10.1007/BF00290149
10.1137/S0097539700381097
10.1007/BF01580444
10.1016/j.jcss.2007.06.019
10.4007/annals.2005.162.439
10.1007/11427186_47
10.1145/502090.502098
10.1145/509907.510017
ContentType Journal Article
Copyright 2011 Elsevier B.V.
2015 INIST-CNRS
Copyright_xml – notice: 2011 Elsevier B.V.
– notice: 2015 INIST-CNRS
DBID 6I.
AAFTH
IQODW
AAYXX
CITATION
7SC
8FD
JQ2
L7M
L~C
L~D
DOI 10.1016/j.dam.2011.10.027
DatabaseName ScienceDirect Open Access Titles
Elsevier:ScienceDirect:Open Access
Pascal-Francis
CrossRef
Computer and Information Systems Abstracts
Technology Research Database
ProQuest Computer Science Collection
Advanced Technologies Database with Aerospace
Computer and Information Systems Abstracts – Academic
Computer and Information Systems Abstracts Professional
DatabaseTitle CrossRef
Computer and Information Systems Abstracts
Technology Research Database
Computer and Information Systems Abstracts – Academic
Advanced Technologies Database with Aerospace
ProQuest Computer Science Collection
Computer and Information Systems Abstracts Professional
DatabaseTitleList Computer and Information Systems Abstracts

DeliveryMethod fulltext_linktorsrc
Discipline Mathematics
Applied Sciences
EISSN 1872-6771
EndPage 203
ExternalDocumentID 10_1016_j_dam_2011_10_027
25335349
S0166218X11004082
GroupedDBID -~X
6I.
AAFTH
ADEZE
AFTJW
AI.
ALMA_UNASSIGNED_HOLDINGS
FA8
FDB
OAUVE
VH1
WUQ
IQODW
AAYXX
CITATION
7SC
8FD
JQ2
L7M
L~C
L~D
ID FETCH-LOGICAL-c403t-427b409eef1985c2d5965e1a3c06275d062c80607a14e8be11a7f4385591b8e53
IEDL.DBID IXB
ISSN 0166-218X
IngestDate Fri Aug 16 22:28:04 EDT 2024
Fri Aug 23 01:40:32 EDT 2024
Sun Oct 22 16:04:27 EDT 2023
Sat Apr 29 22:45:09 EDT 2023
IsDoiOpenAccess true
IsOpenAccess true
IsPeerReviewed true
IsScholarly true
Issue 3
Keywords Weak edge reduction
NP-complete problems
LP-relaxation
Approximation algorithm
Vertex cover problem
Vertex
Edge(graph)
Computer theory
Polynomial approximation
Linear programming
Vertex(graph)
Optimization
Polynomial time
Relaxation
Upper bound
Genetic linkage
NP complete problem
Combinatorics
Performance
Language English
License http://www.elsevier.com/open-access/userlicense/1.0
CC BY 4.0
LinkModel DirectLink
MergedId FETCHMERGED-LOGICAL-c403t-427b409eef1985c2d5965e1a3c06275d062c80607a14e8be11a7f4385591b8e53
Notes ObjectType-Article-2
SourceType-Scholarly Journals-1
ObjectType-Feature-1
content type line 23
OpenAccessLink https://www.sciencedirect.com/science/article/pii/S0166218X11004082
PQID 1010918148
PQPubID 23500
PageCount 7
ParticipantIDs proquest_miscellaneous_1010918148
crossref_primary_10_1016_j_dam_2011_10_027
pascalfrancis_primary_25335349
elsevier_sciencedirect_doi_10_1016_j_dam_2011_10_027
PublicationCentury 2000
PublicationDate 2012-02-01
PublicationDateYYYYMMDD 2012-02-01
PublicationDate_xml – month: 02
  year: 2012
  text: 2012-02-01
  day: 01
PublicationDecade 2010
PublicationPlace Kidlington
PublicationPlace_xml – name: Kidlington
PublicationTitle Discrete Applied Mathematics
PublicationYear 2012
Publisher Elsevier B.V
Elsevier
Publisher_xml – name: Elsevier B.V
– name: Elsevier
References Dinur, Safra (br000030) 2005; 162
Han, Punnen, Ye (br000040) 2009; 37
S. Khot, On the power of unique 2-Prover 1-Round games, in: Pproceedings of 34th ACM Symposium on Theory of Computing, STOC, 2002, pp. 767–775.
E. Asgeirsson, C. Stein, Vertex cover approximations: experiments and observations, in: Proceedings of WEA, 2005, pp. 545–557.
Arora, Bollobàs, Lovàsz, Tourlakis (br000005) 2006; 2
Bar-Yehuda, Even (br000020) 1985; 25
Nemhauser, Trotter (br000085) 1974; 6
Khot, Regev (br000070) 2008; 74
Håstad (br000050) 2001; 48
Halperin (br000035) 2002; 31
Hochbaum (br000055) 1997
Asgeirsson, Stein (br000015) 2007; vol. 4525
B. Harb, The unique games conjecture and some of its implications on inapproximability, Manuscript, May 2005.
Nemhauser, Trotter (br000090) 1975; 8
Karakostas (br000060) 2009; 5
Charikar (br000025) 2002
Monien, Speckenmeyer (br000080) 1985; 22
Kleinberg, Goemans (br000075) 1998; 11
Han (10.1016/j.dam.2011.10.027_br000040) 2009; 37
Hochbaum (10.1016/j.dam.2011.10.027_br000055) 1997
Halperin (10.1016/j.dam.2011.10.027_br000035) 2002; 31
10.1016/j.dam.2011.10.027_br000045
Kleinberg (10.1016/j.dam.2011.10.027_br000075) 1998; 11
Nemhauser (10.1016/j.dam.2011.10.027_br000085) 1974; 6
Bar-Yehuda (10.1016/j.dam.2011.10.027_br000020) 1985; 25
10.1016/j.dam.2011.10.027_br000010
10.1016/j.dam.2011.10.027_br000065
Khot (10.1016/j.dam.2011.10.027_br000070) 2008; 74
Karakostas (10.1016/j.dam.2011.10.027_br000060) 2009; 5
Charikar (10.1016/j.dam.2011.10.027_br000025) 2002
Håstad (10.1016/j.dam.2011.10.027_br000050) 2001; 48
Monien (10.1016/j.dam.2011.10.027_br000080) 1985; 22
Nemhauser (10.1016/j.dam.2011.10.027_br000090) 1975; 8
Asgeirsson (10.1016/j.dam.2011.10.027_br000015) 2007; vol. 4525
Dinur (10.1016/j.dam.2011.10.027_br000030) 2005; 162
Arora (10.1016/j.dam.2011.10.027_br000005) 2006; 2
References_xml – volume: 5
  start-page: 41:1
  year: 2009
  end-page: 41:8
  ident: br000060
  article-title: A better approximation ratio for the vertex cover problem
  publication-title: ACM Transactions on Algorithms
  contributor:
    fullname: Karakostas
– volume: 162
  start-page: 439
  year: 2005
  end-page: 485
  ident: br000030
  article-title: On the hardness of approximating minimum vertex cover biased
  publication-title: Annals of Mathematics
  contributor:
    fullname: Safra
– volume: 48
  start-page: 798
  year: 2001
  end-page: 859
  ident: br000050
  article-title: Some optimal inapproximability results
  publication-title: Journal of the Association of Computing Machinery
  contributor:
    fullname: Håstad
– volume: 6
  start-page: 48
  year: 1974
  end-page: 61
  ident: br000085
  article-title: Properties of vertex packing and independence system polyhedra
  publication-title: Mathematical Programming
  contributor:
    fullname: Trotter
– start-page: 94
  year: 1997
  end-page: 143
  ident: br000055
  article-title: Approximating covering and packing problems: set cover, independent set, and related problems
  publication-title: Approximation Algorithms for NP-Hard Problems
  contributor:
    fullname: Hochbaum
– volume: 22
  start-page: 115
  year: 1985
  end-page: 123
  ident: br000080
  article-title: Ramsey numbers and an approximation algorithm for the vertex cover problem
  publication-title: Acta Informatica
  contributor:
    fullname: Speckenmeyer
– volume: 37
  start-page: 181
  year: 2009
  end-page: 186
  ident: br000040
  article-title: A polynomial time
  publication-title: Operations Research Letters
  contributor:
    fullname: Ye
– volume: 31
  start-page: 1608
  year: 2002
  end-page: 1623
  ident: br000035
  article-title: Improved approximation algorithms for the vertex cover problem in graphs and hypergraphs
  publication-title: SIAM Journal of Computing
  contributor:
    fullname: Halperin
– volume: 74
  start-page: 335
  year: 2008
  end-page: 349
  ident: br000070
  article-title: Vertex cover might be hard to approximate to within
  publication-title: Journal of Computer and System Sciences
  contributor:
    fullname: Regev
– start-page: 616
  year: 2002
  end-page: 620
  ident: br000025
  article-title: On semidefinite programming relaxations for graph coloring and vertex cover
  publication-title: Proceedings of SODA
  contributor:
    fullname: Charikar
– volume: vol. 4525
  start-page: 285
  year: 2007
  end-page: 296
  ident: br000015
  publication-title: Vertex Cover Approximations on Random Graphs
  contributor:
    fullname: Stein
– volume: 8
  start-page: 232
  year: 1975
  end-page: 248
  ident: br000090
  article-title: Vertex packings: structural properties and algorithms
  publication-title: Mathematical Programming
  contributor:
    fullname: Trotter
– volume: 25
  start-page: 27
  year: 1985
  end-page: 45
  ident: br000020
  article-title: A local-ratio theorem for approximating the weighted vertex cover problem
  publication-title: Annals of Discrete Mathematics
  contributor:
    fullname: Even
– volume: 2
  start-page: 19
  year: 2006
  end-page: 51
  ident: br000005
  article-title: Proving integrality gaps without knowing the linear program
  publication-title: Theory of Computing
  contributor:
    fullname: Tourlakis
– volume: 11
  start-page: 196
  year: 1998
  end-page: 204
  ident: br000075
  article-title: The Lovøasz theta function and a semidefinite programming relaxation of vertex cover
  publication-title: SIAM Journal of Discrete mathematics
  contributor:
    fullname: Goemans
– volume: 5
  start-page: 41:1
  year: 2009
  ident: 10.1016/j.dam.2011.10.027_br000060
  article-title: A better approximation ratio for the vertex cover problem
  publication-title: ACM Transactions on Algorithms
  doi: 10.1145/1597036.1597045
  contributor:
    fullname: Karakostas
– volume: 6
  start-page: 48
  year: 1974
  ident: 10.1016/j.dam.2011.10.027_br000085
  article-title: Properties of vertex packing and independence system polyhedra
  publication-title: Mathematical Programming
  doi: 10.1007/BF01580222
  contributor:
    fullname: Nemhauser
– volume: vol. 4525
  start-page: 285
  year: 2007
  ident: 10.1016/j.dam.2011.10.027_br000015
  contributor:
    fullname: Asgeirsson
– volume: 11
  start-page: 196
  year: 1998
  ident: 10.1016/j.dam.2011.10.027_br000075
  article-title: The Lovøasz theta function and a semidefinite programming relaxation of vertex cover
  publication-title: SIAM Journal of Discrete mathematics
  doi: 10.1137/S0895480195287541
  contributor:
    fullname: Kleinberg
– volume: 2
  start-page: 19
  year: 2006
  ident: 10.1016/j.dam.2011.10.027_br000005
  article-title: Proving integrality gaps without knowing the linear program
  publication-title: Theory of Computing
  doi: 10.4086/toc.2006.v002a002
  contributor:
    fullname: Arora
– volume: 25
  start-page: 27
  year: 1985
  ident: 10.1016/j.dam.2011.10.027_br000020
  article-title: A local-ratio theorem for approximating the weighted vertex cover problem
  publication-title: Annals of Discrete Mathematics
  contributor:
    fullname: Bar-Yehuda
– volume: 37
  start-page: 181
  year: 2009
  ident: 10.1016/j.dam.2011.10.027_br000040
  article-title: A polynomial time 32-approximation algorithm for the vertex cover problem on a class of graphs
  publication-title: Operations Research Letters
  doi: 10.1016/j.orl.2009.01.010
  contributor:
    fullname: Han
– volume: 22
  start-page: 115
  year: 1985
  ident: 10.1016/j.dam.2011.10.027_br000080
  article-title: Ramsey numbers and an approximation algorithm for the vertex cover problem
  publication-title: Acta Informatica
  doi: 10.1007/BF00290149
  contributor:
    fullname: Monien
– start-page: 616
  year: 2002
  ident: 10.1016/j.dam.2011.10.027_br000025
  article-title: On semidefinite programming relaxations for graph coloring and vertex cover
  publication-title: Proceedings of SODA
  contributor:
    fullname: Charikar
– volume: 31
  start-page: 1608
  year: 2002
  ident: 10.1016/j.dam.2011.10.027_br000035
  article-title: Improved approximation algorithms for the vertex cover problem in graphs and hypergraphs
  publication-title: SIAM Journal of Computing
  doi: 10.1137/S0097539700381097
  contributor:
    fullname: Halperin
– ident: 10.1016/j.dam.2011.10.027_br000045
– volume: 8
  start-page: 232
  year: 1975
  ident: 10.1016/j.dam.2011.10.027_br000090
  article-title: Vertex packings: structural properties and algorithms
  publication-title: Mathematical Programming
  doi: 10.1007/BF01580444
  contributor:
    fullname: Nemhauser
– start-page: 94
  year: 1997
  ident: 10.1016/j.dam.2011.10.027_br000055
  article-title: Approximating covering and packing problems: set cover, independent set, and related problems
  contributor:
    fullname: Hochbaum
– volume: 74
  start-page: 335
  year: 2008
  ident: 10.1016/j.dam.2011.10.027_br000070
  article-title: Vertex cover might be hard to approximate to within 2−ϵ
  publication-title: Journal of Computer and System Sciences
  doi: 10.1016/j.jcss.2007.06.019
  contributor:
    fullname: Khot
– volume: 162
  start-page: 439
  year: 2005
  ident: 10.1016/j.dam.2011.10.027_br000030
  article-title: On the hardness of approximating minimum vertex cover biased
  publication-title: Annals of Mathematics
  doi: 10.4007/annals.2005.162.439
  contributor:
    fullname: Dinur
– ident: 10.1016/j.dam.2011.10.027_br000010
  doi: 10.1007/11427186_47
– volume: 48
  start-page: 798
  year: 2001
  ident: 10.1016/j.dam.2011.10.027_br000050
  article-title: Some optimal inapproximability results
  publication-title: Journal of the Association of Computing Machinery
  doi: 10.1145/502090.502098
  contributor:
    fullname: Håstad
– ident: 10.1016/j.dam.2011.10.027_br000065
  doi: 10.1145/509907.510017
SSID ssj0001218
ssj0000186
ssj0006644
Score 1.9869277
Snippet In this paper we show that the problem of identifying an edge ( i , j ) of a graph G such that there exists an optimal vertex cover S of G containing exactly...
In this paper we show that the problem of identifying an edge (i,j) of a graph G such that there exists an optimal vertex cover S of G containing exactly one...
SourceID proquest
crossref
pascalfrancis
elsevier
SourceType Aggregation Database
Index Database
Publisher
StartPage 197
SubjectTerms Algorithmics. Computability. Computer arithmetics
Algorithms
Applied sciences
Approximation
Approximation algorithm
Approximations and expansions
Combinatorics
Combinatorics. Ordered structures
Computer science; control theory; systems
Exact sciences and technology
Graphs
LP-relaxation
Mathematical analysis
Mathematics
NP-complete problems
Optimization
Representations
Sciences and techniques of general use
Theoretical computing
Upper bounds
Vertex cover problem
Weak edge reduction
Title Strong and weak edges of a graph and linkages with the vertex cover problem
URI https://dx.doi.org/10.1016/j.dam.2011.10.027
https://search.proquest.com/docview/1010918148
Volume 160
hasFullText 1
inHoldings 1
isFullTextHit
isPrint
link http://utb.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwnV3NT9swFH9icGFCaBubKB-VkThNCo1jO3WPUIG6FdA0YOotcmwHFURa0SI48bfznpOwoSEOXGLFkW3lOXnf_j2A3cJpK63jkVVJFw0U04u08nGUp6j9c8Nj4UK2xWk6uJA_R2q0AP3mLAylVda8v-LpgVvXPZ2amp3peNw5Q2UlRQE1CqBnKMmQDwvFwyG-0cE_EFKEj7bcOF3-xhhQ1soa-TuNaJ4m5hmyv5y5qfA9KfWLSs68LrVWpmaGtCyqIhj_8fMgpI4-wWqtXbL96gU-w4Ivv8DHk2do1tkaDM_I-X3JTOnYvTfXjBxqMzYpmGEBvTo8obiuoX7y0zIczqhus39gllI-WV2G5itcHB2e9wdRXVEhsjIW80gm3RwNOu8L3tPKJk71UuW5ETagFTu8Wh2ncddw6XXucbe6hRQazQ6ea6_EN1gsJ6VfB-a8dIXQeSqkkjhIa-NznEwVNlbO8RZ8byiWTSvgjKzJKLvKkLwZkZe6kLwtkA1Nsxe7nyFjf2tY-wX9nxdKUIlVQvZasNNsSIa_DcVCTOkndzOaEDUljcbgxvvW3oRlvEuqBO4tWJzf3vlt1E_meRs-7D3yNiztH_wZHlPb_338i9ofw8FpO3yeTwD845Q
link.rule.ids 315,783,787,3513,4509,24128,27581,27936,27937,45597,45675,45691,45886
linkProvider Elsevier
linkToHtml http://utb.summon.serialssolutions.com/2.0.0/link/0/eLvHCXMwnV1LTwIxEJ4gHMQY4zPiA2viyWTDPtqleyREAoJcgITbptt2DRoXIhD9-U73gRqNBy976KZt9ms7M52Z_QbgJlZcUqkcSzK3iRcUEVicaduKfLT-HeHYnkqzLYZ-d0Lvp2xagnbxL4xJq8xlfybTU2mdtzRyNBuL2awxQmPFRwU1TUnPUJNtQQWtgQBPZ6XV63eHX1ikDEVatfC7fIYZUN3SnPzbt8xQRdgzTQBT4iWj-DTZX6bqzO-Ka3chlghnnNXB-CHSUz3V2Ye93MAkrewbDqCkk0PYediwsy6PoD8y_u9HIhJF3rR4JsantiTzmAiSElinb0xoV5h246ol2J2Y0s36nUiT9UnySjTHMOncjdtdKy-qYElqeyuLus0I73Rax07AmXQVC3ymHeHJlLBY4VNy27ebwqGaRxoXrBlTj-PNw4m4Zt4JlJN5ok-BKE1V7PHI9yij2IlzoSMcjMXSZko5NbgtEAsXGXdGWCSVPYUIb2jgNU0Ibw1ogWn4bQOEKNv_6lb_hv9mIhftWObRoAbXxYKEeHJMOEQker5emgHRWOJ4Hzz739xXsN0dPwzCQW_YP4cqvnGzfO4LKK9e1_oSzZVVVM-34wdl0-Ic
openUrl ctx_ver=Z39.88-2004&ctx_enc=info%3Aofi%2Fenc%3AUTF-8&rfr_id=info%3Asid%2Fsummon.serialssolutions.com&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Strong+and+weak+edges+of+a+graph+and+linkages+with+the+vertex+cover+problem&rft.jtitle=Discrete+applied+mathematics&rft.au=QIAOMING+HAN&rft.au=PUNNEN%2C+Abraham+P&rft.date=2012-02-01&rft.pub=Elsevier&rft.issn=0166-218X&rft.eissn=1872-6771&rft.volume=160&rft.issue=3&rft.spage=197&rft.epage=203&rft_id=info:doi/10.1016%2Fj.dam.2011.10.027&rft.externalDBID=n%2Fa&rft.externalDocID=25335349
thumbnail_l http://covers-cdn.summon.serialssolutions.com/index.aspx?isbn=/lc.gif&issn=0166-218X&client=summon
thumbnail_m http://covers-cdn.summon.serialssolutions.com/index.aspx?isbn=/mc.gif&issn=0166-218X&client=summon
thumbnail_s http://covers-cdn.summon.serialssolutions.com/index.aspx?isbn=/sc.gif&issn=0166-218X&client=summon