World's Best Scientists 2026 revealed!
VIEW LIST
W. A. Zajc

D-Index & Metrics

Discipline name D-Index World Ranking Current World Ranking National Ranking Current National Ranking Publications Citations
Physics 102 1545 1467 813 760 458 40129

W. A. Zajc publications per year

The chart shows the history of publications by W. A. Zajc between 1973 and 2021, highlighting the no. of papers published in each year and offering an overview of the publication velocity of this scholar. W. A. Zajc published across 49 years, from 1973 to 2021, averaging 8.9 papers a year. Output peaked at 37 publications in 2014. 18 of the 437 publications appeared in the last two years.

No. of publications
10 20 30
Bar chart. Horizontal axis: year, 1973 to 2021. Vertical axis: number of publications, 0 to 37. Peak 37 publications in 2014. 1973: 1 publication 1974: 0 publications 1975: 0 publications 1976: 0 publications 1977: 0 publications 1978: 0 publications 1979: 0 publications 1980: 0 publications 1981: 1 publication 1982: 3 publications 1983: 6 publications 1984: 4 publications 1985: 6 publications 1986: 6 publications 1987: 4 publications 1988: 7 publications 1989: 4 publications 1990: 3 publications 1991: 9 publications 1992: 7 publications 1993: 7 publications 1994: 5 publications 1995: 6 publications 1996: 4 publications 1997: 4 publications 1998: 10 publications 1999: 9 publications 2000: 2 publications 2001: 8 publications 2002: 16 publications 2003: 17 publications 2004: 14 publications 2005: 11 publications 2006: 23 publications 2007: 21 publications 2008: 18 publications 2009: 16 publications 2010: 14 publications 2011: 18 publications 2012: 15 publications 2013: 13 publications 2014: 37 publications 2015: 16 publications 2016: 15 publications 2017: 10 publications 2018: 19 publications 2019: 10 publications 2020: 10 publications 2021: 8 publications
1973 2021

437 publications in total across all disciplines

View publications per year as a table
W. A. Zajc: publications per year, 1973 to 2021
Year Publications
1973 1
1974 0
1975 0
1976 0
1977 0
1978 0
1979 0
1980 0
1981 1
1982 3
1983 6
1984 4
1985 6
1986 6
1987 4
1988 7
1989 4
1990 3
1991 9
1992 7
1993 7
1994 5
1995 6
1996 4
1997 4
1998 10
1999 9
2000 2
2001 8
2002 16
2003 17
2004 14
2005 11
2006 23
2007 21
2008 18
2009 16
2010 14
2011 18
2012 15
2013 13
2014 37
2015 16
2016 15
2017 10
2018 19
2019 10
2020 10
2021 8
Total 437
Download as CSV

W. A. Zajc publication distribution in Physics in 2026

The chart shows the distribution of publications by all Research.com ranked scientists in the field of Physics in 2026. The highlighted bar marks where W. A. Zajc sits on this spectrum.

No. of scientists
50 100 150
Bar chart with 70 bars. Horizontal axis: publications, 103–122 to 1,469+. Vertical axis: number of scientists, 0 to 162. Most scientists, 162, have 323–342 publications. The last bar groups every scientist with 1,469 publications or more. The highlighted bar, 443–462 publications, is where this scientist sits. 103–122 publications: 7 scientists 123–142 publications: 10 scientists 143–162 publications: 31 scientists 163–182 publications: 35 scientists 183–202 publications: 53 scientists 203–222 publications: 81 scientists 223–242 publications: 85 scientists 243–262 publications: 112 scientists 263–282 publications: 114 scientists 283–302 publications: 126 scientists 303–322 publications: 136 scientists 323–342 publications: 162 scientists 343–362 publications: 155 scientists 363–382 publications: 156 scientists 383–402 publications: 134 scientists 403–422 publications: 145 scientists 423–442 publications: 147 scientists 443–462 publications: 131 scientists 463–482 publications: 131 scientists 483–502 publications: 116 scientists 503–522 publications: 106 scientists 523–542 publications: 103 scientists 543–562 publications: 87 scientists 563–582 publications: 84 scientists 583–602 publications: 94 scientists 603–622 publications: 70 scientists 623–642 publications: 76 scientists 643–662 publications: 60 scientists 663–682 publications: 54 scientists 683–702 publications: 60 scientists 703–722 publications: 48 scientists 723–742 publications: 64 scientists 743–762 publications: 48 scientists 763–782 publications: 37 scientists 783–802 publications: 43 scientists 803–822 publications: 34 scientists 823–842 publications: 36 scientists 843–862 publications: 32 scientists 863–882 publications: 32 scientists 883–902 publications: 31 scientists 903–922 publications: 25 scientists 923–942 publications: 15 scientists 943–962 publications: 24 scientists 963–982 publications: 13 scientists 983–1,002 publications: 21 scientists 1,003–1,022 publications: 21 scientists 1,023–1,042 publications: 16 scientists 1,043–1,062 publications: 9 scientists 1,063–1,082 publications: 19 scientists 1,083–1,102 publications: 11 scientists 1,103–1,122 publications: 17 scientists 1,123–1,142 publications: 11 scientists 1,143–1,162 publications: 7 scientists 1,163–1,182 publications: 4 scientists 1,183–1,202 publications: 10 scientists 1,203–1,222 publications: 8 scientists 1,223–1,242 publications: 16 scientists 1,243–1,262 publications: 4 scientists 1,263–1,282 publications: 10 scientists 1,283–1,302 publications: 5 scientists 1,303–1,322 publications: 7 scientists 1,323–1,342 publications: 4 scientists 1,343–1,362 publications: 8 scientists 1,363–1,382 publications: 6 scientists 1,383–1,402 publications: 7 scientists 1,403–1,422 publications: 3 scientists 1,423–1,442 publications: 4 scientists 1,443–1,462 publications: 4 scientists 1,463–1,468 publications: 3 scientists 1,469+ publications: 100 scientists
103–122 publications 1,469+

This scientist: 458 publications — 49th percentile

49% of scientists in this discipline score the same or lower.

The last bar groups every scientist with 1,469 publications or more.

View publications distribution as a table
Number of Physics scientists by publication count, Research.com 2026 ranking edition. Based on 3,678 ranked scientists.
Publications Scientists This scientist
103–122 7
123–142 10
143–162 31
163–182 35
183–202 53
203–222 81
223–242 85
243–262 112
263–282 114
283–302 126
303–322 136
323–342 162
343–362 155
363–382 156
383–402 134
403–422 145
423–442 147
443–462 131 458
463–482 131
483–502 116
503–522 106
523–542 103
543–562 87
563–582 84
583–602 94
603–622 70
623–642 76
643–662 60
663–682 54
683–702 60
703–722 48
723–742 64
743–762 48
763–782 37
783–802 43
803–822 34
823–842 36
843–862 32
863–882 32
883–902 31
903–922 25
923–942 15
943–962 24
963–982 13
983–1,002 21
1,003–1,022 21
1,023–1,042 16
1,043–1,062 9
1,063–1,082 19
1,083–1,102 11
1,103–1,122 17
1,123–1,142 11
1,143–1,162 7
1,163–1,182 4
1,183–1,202 10
1,203–1,222 8
1,223–1,242 16
1,243–1,262 4
1,263–1,282 10
1,283–1,302 5
1,303–1,322 7
1,323–1,342 4
1,343–1,362 8
1,363–1,382 6
1,383–1,402 7
1,403–1,422 3
1,423–1,442 4
1,443–1,462 4
1,463–1,468 3
1,469+ 100
Download as CSV

W. A. Zajc D-index placement in Physics in 2026

The chart shows the D-index (discipline H-index) distribution of Physics scientists ranked by Research.com in 2026. The highlighted bar marks where W. A. Zajc sits on this spectrum.

No. of scientists
50 100 150
Bar chart with 59 bars. Horizontal axis: D-Index, 70–71 to 185+. Vertical axis: number of scientists, 0 to 167. Most scientists, 167, have 80–81 D-Index. The last bar groups every scientist with 185 D-Index or more. The highlighted bar, 102–103 D-Index, is where this scientist sits. 70–71 D-Index: 76 scientists 72–73 D-Index: 110 scientists 74–75 D-Index: 143 scientists 76–77 D-Index: 153 scientists 78–79 D-Index: 144 scientists 80–81 D-Index: 167 scientists 82–83 D-Index: 167 scientists 84–85 D-Index: 166 scientists 86–87 D-Index: 132 scientists 88–89 D-Index: 155 scientists 90–91 D-Index: 134 scientists 92–93 D-Index: 137 scientists 94–95 D-Index: 102 scientists 96–97 D-Index: 112 scientists 98–99 D-Index: 110 scientists 100–101 D-Index: 116 scientists 102–103 D-Index: 97 scientists 104–105 D-Index: 103 scientists 106–107 D-Index: 87 scientists 108–109 D-Index: 90 scientists 110–111 D-Index: 67 scientists 112–113 D-Index: 78 scientists 114–115 D-Index: 75 scientists 116–117 D-Index: 67 scientists 118–119 D-Index: 69 scientists 120–121 D-Index: 60 scientists 122–123 D-Index: 59 scientists 124–125 D-Index: 53 scientists 126–127 D-Index: 42 scientists 128–129 D-Index: 41 scientists 130–131 D-Index: 33 scientists 132–133 D-Index: 32 scientists 134–135 D-Index: 45 scientists 136–137 D-Index: 19 scientists 138–139 D-Index: 24 scientists 140–141 D-Index: 28 scientists 142–143 D-Index: 31 scientists 144–145 D-Index: 22 scientists 146–147 D-Index: 20 scientists 148–149 D-Index: 12 scientists 150–151 D-Index: 16 scientists 152–153 D-Index: 24 scientists 154–155 D-Index: 23 scientists 156–157 D-Index: 15 scientists 158–159 D-Index: 15 scientists 160–161 D-Index: 11 scientists 162–163 D-Index: 17 scientists 164–165 D-Index: 12 scientists 166–167 D-Index: 11 scientists 168–169 D-Index: 9 scientists 170–171 D-Index: 9 scientists 172–173 D-Index: 11 scientists 174–175 D-Index: 4 scientists 176–177 D-Index: 8 scientists 178–179 D-Index: 5 scientists 180–181 D-Index: 3 scientists 182–183 D-Index: 4 scientists 184 D-Index: 4 scientists 185+ D-Index: 99 scientists
70–71 D-Index 185+

This scientist: 102 D-Index — 59th percentile

59% of scientists in this discipline score the same or lower.

The last bar groups every scientist with 185 D-Index or more.

View D-Index distribution as a table
Number of Physics scientists by D-index, Research.com 2026 ranking edition. Based on 3,678 ranked scientists.
D-Index Scientists This scientist
70–71 76
72–73 110
74–75 143
76–77 153
78–79 144
80–81 167
82–83 167
84–85 166
86–87 132
88–89 155
90–91 134
92–93 137
94–95 102
96–97 112
98–99 110
100–101 116
102–103 97 102
104–105 103
106–107 87
108–109 90
110–111 67
112–113 78
114–115 75
116–117 67
118–119 69
120–121 60
122–123 59
124–125 53
126–127 42
128–129 41
130–131 33
132–133 32
134–135 45
136–137 19
138–139 24
140–141 28
142–143 31
144–145 22
146–147 20
148–149 12
150–151 16
152–153 24
154–155 23
156–157 15
158–159 15
160–161 11
162–163 17
164–165 12
166–167 11
168–169 9
170–171 9
172–173 11
174–175 4
176–177 8
178–179 5
180–181 3
182–183 4
184 4
185+ 99
Download as CSV

Research.com Recognitions

  • 2014 - Tom W. Bonner Prize in Nuclear Physics, American Physical Society
  • 2011 - Fellow of the American Association for the Advancement of Science (AAAS)
  • 1997 - Fellow of American Physical Society (APS) Citation For his landmark contribution to experimental studies of twoboson correlation in relativistic heavyion collisions

Overview

W. A. Zajc is affiliated with Columbia University in the United States. Their academic career includes recognition by major scientific societies, reflecting an active role in the physics community.

Among the awards received, W. A. Zajc was honored with the Tom W. Bonner Prize in Nuclear Physics awarded by the American Physical Society in 2014. Earlier, they were named a Fellow of the American Association for the Advancement of Science (AAAS) in 2011. Additionally, they were elected as a Fellow of the American Physical Society (APS) in 1997, with a citation specifying their contribution to experimental studies involving two-boson correlation in relativistic heavy-ion collisions.

This recognition highlights their involvement in nuclear physics, particularly in experimental approaches to high-energy particle collision phenomena. The focus on two-boson correlations situates their work within the broader field of relativistic heavy-ion physics, which explores the properties of nuclear matter under extreme conditions.

While data on specific publications, co-authors, or detailed research topics beyond these contributions is not provided, the awards and primary affiliation place W. A. Zajc as an active contributor to the nuclear physics research community at Columbia University.

Best Publications

  • Formation of dense partonic matter in relativistic nucleus–nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration

    K. Adcox;S. S. Adler;S. Afanasiev;C. Aidala;C. Aidala

  • Suppression of hadrons with large transverse momentum in central Au + Au collisions at √sNN = 130 GeV

    K. Adcox;S. S. Adler;N. N. Ajitanand;Y. Akiba

  • PHENIX detector overview

    K. Adcox;S.S. Adler;M. Aizama;N.N. Ajitanand

  • Identified charged particle spectra and yields in Au + Au collisions at √sNN = 200 GeV

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Elliptic flow of identified hadrons in [formula presented] collisions at [formula presented]

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Suppressed π0 Production at Large Transverse Momentum in Central Au + Au Collisions at √sNN = 200 GeV

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Energy loss and flow of heavy quarks in Au+Au collisions at sNN=200GeV

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • J/psi production versus centrality, transverse momentum, and rapidity in Au+Au collisions at root S-NN=200 GeV

    A. Adare;S. Afanasiev;C. Aidala;N.N. Ajitanand

  • Scaling properties of azimuthal anisotropy in Au+Au and Cu+Cu collisions at sNN=200GeV

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Suppressedπ0Production at Large Transverse Momentum in CentralAu+AuCollisions atsNN=200GeV

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • J/ψProduction versus Centrality, Transverse Momentum, andRapidity inAu+AuCollisions atsNN=200GeV

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Enhanced Production of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV and Implications for the Initial Temperature

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Absence of suppression in particle production at large transverse momentum in √sNN = 200 GeV d + Au collisions

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Detailed measurement of the e+e- pair continuum in p+p and Au+Au collisions at √sNN = 200 GeV and implications for direct photon production

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Suppression Pattern of Neutral Pions at High Transverse Momentum in Au plus Au Collisions at root S-NN=200 GeV and Constraints on Medium Transport Coefficients

    A. Adare;S. Afanasiev;C. Aidala;N.N. Ajitanand

  • Nuclear modification of electron spectra and implications for heavy quark energy loss in Au+Au collisions at sNN=200GeV

    S. S. Adler;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Measurements of higher order flow harmonics in Au+Au collisions at √sNN=200GeV

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Heavy-quark production in p + p and energy loss and flow of heavy quarks in Au + Au collisions at √sNN=200 GeV

    A. Adare;S. Afanasiev;C. Aidala;N. N. Ajitanand

  • Centrality dependence of π+/-, K+/-, p, and p̄ production from √sNN = 130 GeV Au + Au collisions at RHIC

    K. Adcox;S. S. Adler;N. N. Ajitanand;Y. Akiba

  • The PHENIX Collaboration

    A. Adare;S. Afanasiev;C. Aidala;C. Aidala;N. N. Ajitanand

Frequent Co-Authors

M. J. Tannenbaum
M. J. Tannenbaum Brookhaven National Laboratory
R. Seto
R. Seto University of California, Riverside
D. P. Morrison
D. P. Morrison Brookhaven National Laboratory
Ryugo S. Hayano
Ryugo S. Hayano University of Tokyo
E. O'Brien
E. O'Brien Brookhaven National Laboratory
P. L. McGaughey
P. L. McGaughey Los Alamos National Laboratory
S. Nagamiya
S. Nagamiya Japan Atomic Energy Agency
C. A. Aidala
C. A. Aidala University of Michigan–Ann Arbor
C. L. Woody
C. L. Woody Brookhaven National Laboratory
T. C. Awes
T. C. Awes Oak Ridge National Laboratory

External Links

Wikipedia of W. A. Zajc Personal website of W. A. Zajc

If you think any of the details on this page are incorrect, let us know.

Report an issue

We appreciate your kind effort to assist us to improve this page, it would be helpful providing us with as much detail as possible in the text box below:

Best Scientists Citing W. A. Zajc

Bedangadas Mohanty

Bedangadas Mohanty

National Institute of Science Education and Research

Publications: 290

Zubayer Ahammed

Zubayer Ahammed

Variable Energy Cyclotron Centre

Publications: 287

Madan M. Aggarwal

Madan M. Aggarwal

Panjab University

Publications: 276

M. A. Lisa

M. A. Lisa

The Ohio State University

Publications: 216

Jovan Milosevic

Jovan Milosevic

University of Belgrade

Publications: 214

Trine Spedstad Tveter

Trine Spedstad Tveter

University of Oslo

Publications: 207

Joakim Nystrand

Joakim Nystrand

University of Bergen

Publications: 204

Dieter Røhrich

Dieter Røhrich

University of Bergen

Publications: 201

Dagmar Adamová

Dagmar Adamová

Czech Academy of Sciences

Publications: 194

Johan Alme

Johan Alme

University of Bergen

Publications: 192

Kristin Fanebust Hetland

Kristin Fanebust Hetland

Western Norway University of Applied Sciences

Publications: 189

Jørgen André Lien

Jørgen André Lien

University of South-Eastern Norway

Publications: 188

Sergey Voloshin

Sergey Voloshin

Wayne State University

Publications: 187

Kjetil Ullaland

Kjetil Ullaland

University of Bergen

Publications: 186

Jon Christopher Wikne

Jon Christopher Wikne

University of Oslo

Publications: 186

Matthias Richter

Matthias Richter

Ruhr University Bochum

Publications: 186

Trending Scientists

Vasil M. Garamus

Vasil M. Garamus

Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research

Elizabeth M. Gillanders

Elizabeth M. Gillanders

National Institutes of Health

Shanhui Fan

Shanhui Fan

Stanford University

Ulrich Reininghaus

Ulrich Reininghaus

Heidelberg University

Jeffrey Roelofs

Jeffrey Roelofs

Maastricht University

Sally E. Thorpe

Sally E. Thorpe

Natural Environment Research Council

Jonathan Widdicombe

Jonathan Widdicombe

University of California, Davis

Ilmo E. Hassinen

Ilmo E. Hassinen

University of Oulu

Ruiqin Zhong

Ruiqin Zhong

University of Georgia

Linjun Yang

Linjun Yang

Microsoft (United States)

Mariana Valverde

Mariana Valverde

University of Toronto

Yunguo Liu

Yunguo Liu

Hunan University

Michael Feig

Michael Feig

Michigan State University

Rabindra Nepal

Rabindra Nepal

University of Wollongong

Pierfrancesco Tassone

Pierfrancesco Tassone

Magna Graecia University

Shing Yip Lee

Shing Yip Lee

Chinese University of Hong Kong

Related Physics Rankings & Guides

2027 How To Become a Paleontologist? Salary & Career Paths

2027 How To Become a Paleontologist? Salary & Career Paths
2027 Fastest Online Urban Planning Degree Programs You Can Finish in Under 2 Years

2027 Fastest Online Urban Planning Degree Programs You Can Finish in Under 2 Years
2027 Most Affordable Online Physics Degree Programs

2027 Most Affordable Online Physics Degree Programs
2027 Admission Requirements for Physics Degree Programs

2027 Admission Requirements for Physics Degree Programs
2027 Online Photography Degree Programs for Veterans: GI Bill Benefits, Costs & Top Considerations

2027 Online Photography Degree Programs for Veterans: GI Bill Benefits, Costs & Top Considerations
2027 Best Online Physics Degree Programs

2027 Best Online Physics Degree Programs
2027 Best Online Space Studies Degree Programs

2027 Best Online Space Studies Degree Programs
2027 Most Affordable Online Space Studies Degree Programs

2027 Most Affordable Online Space Studies Degree Programs
2027 Online Photography Degree Programs Costs: Tuition & Fees

2027 Online Photography Degree Programs Costs: Tuition & Fees

Recently Published Articles

2027 How Long Does It Take to Be a Teacher in Arizona?

2027 How Long Does It Take to Be a Teacher in Arizona?
2027 Reasons to Get Your DNP Degree

2027 Reasons to Get Your DNP Degree
2027 Online Neurodiagnostic Technology Degree Programs With No Personal Statement or Admissions Essay Required

2027 Online Neurodiagnostic Technology Degree Programs With No Personal Statement or Admissions Essay Required
2027 Different Types of Geographic Information Systems Degrees and Their Salaries

2027 Different Types of Geographic Information Systems Degrees and Their Salaries
2027 Admission Requirements for Machine Learning Degree Programs

2027 Admission Requirements for Machine Learning Degree Programs
2027 Best Marriage and Family Therapy (MFT) Programs in Indiana: Online & Campus

2027 Best Marriage and Family Therapy (MFT) Programs in Indiana: Online & Campus
2027 Best Online MBA Programs for Parents

2027 Best Online MBA Programs for Parents
2027 Online Biology Degree Programs for Veterans: GI Bill Benefits, Costs & Top Considerations

2027 Online Biology Degree Programs for Veterans: GI Bill Benefits, Costs & Top Considerations
2027 What Can You Do with a Master's in Special Education

2027 What Can You Do with a Master's in Special Education
2027 How to Become a Private School Teacher in Missouri: Requirements & Certification

2027 How to Become a Private School Teacher in Missouri: Requirements & Certification
2027 Fine Arts Degree Coursework Explained: What Classes Can You Expect to Take?

2027 Fine Arts Degree Coursework Explained: What Classes Can You Expect to Take?
2027 How Much Does a Game Programming Degree Program Cost? Tuition, Fees & Total Expense Breakdown

2027 How Much Does a Game Programming Degree Program Cost? Tuition, Fees & Total Expense Breakdown
2027 One-Year Online Early Childhood Education Master's Degree Programs: Accelerated Options, Costs & Outcomes

2027 One-Year Online Early Childhood Education Master's Degree Programs: Accelerated Options, Costs & Outcomes
2027 Sports Analytics Degree Outlook Through 2030: Enrollment, Salary, and Hiring Projections

2027 Sports Analytics Degree Outlook Through 2030: Enrollment, Salary, and Hiring Projections
2027 Best BSN to DNP Programs in Louisiana: Online & Campus

2027 Best BSN to DNP Programs in Louisiana: Online & Campus
2027 Medical Billing and Coding Certification: Specialty Certifications to Consider

2027 Medical Billing and Coding Certification: Specialty Certifications to Consider
2027 What Prerequisites Do You Need for a Theology Master's Degree? Entry Requirements, Credits & Eligibility Rules

2027 What Prerequisites Do You Need for a Theology Master's Degree? Entry Requirements, Credits & Eligibility Rules
2027 What Can You Do with an Early Childhood Education Master's Degree? Careers, Salaries & Growth

2027 What Can You Do with an Early Childhood Education Master's Degree? Careers, Salaries & Growth
2027 Most Popular Concentrations in Biology Degrees

2027 Most Popular Concentrations in Biology Degrees
2027 How to Become a Clinical Trials Auditor: Education, Salary, and Job Outlook

2027 How to Become a Clinical Trials Auditor: Education, Salary, and Job Outlook
2027 How to Become a Substance Abuse Counselor in Tucson, AZ: Requirements & Certification

2027 How to Become a Substance Abuse Counselor in Tucson, AZ: Requirements & Certification