FLAW3D: A Trojan-Based Cyber Attack on the Physical Outcomes of Additive Manufacturing
Open accessAbstract
Additive manufacturing (AM) systems such as 3-D printers use inexpensive microcontrollers that rarely feature cybersecurity defenses. This is a risk, especially given the rising threat landscape within the larger digital manufacturing domain. In this work, we demonstrate this risk by presenting the design and study of a malicious Trojan (the FLAW3D bootloader) for AVR-based Marlin-compatible 3-D printers ($>$100 commercial models). We show that the Trojan can hide from programming tools, and even within tight design constraints (less than 1.7 KB in size), it can compromise the quality of additively manufactured prints and reduce tensile strengths by up to 50%.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
Manipulating filament extrusion speed during printing causes localized variations in filament width, with some regions thicker and others thinner.
“It is also possible to target the speed of motion. In such attacks the adversary manipulates the filament extrusion speed during printing, causing localized variations in filament width. Specifically, some regions of the printed object receive more filament, making them thicker, while other regions receive less, resulting in thinner sections[28,27,9,24].”
From Firewall3D: A Hardware Firewall for Defending 3D Printers Against Firmware Attacks (2026) · cites this paper as [24]
Cites
Hardware Trojan attacks: Threat analysis and countermeasures
Bhunia, S., Hsiao, M. S., Banga, M., & Narasimhan, S. (2014) · Proceedings of the IEEE · doi:10.1109/jproc.2014.2334493 · Cited by 766 · see citing works
RepRap – the replicating rapid prototyper
Jones, R., Haufe, P., Sells, E., Iravani, P., Olliver, V., Palmer, C., & Bowyer, A. (2011) · Robotica · doi:10.1017/s026357471000069x · Cited by 740 · see citing works
Trusted Execution Environment: What It is, and What It is Not
Sabt, M., Achemlal, M., & Bouabdallah, A. (2015) · 2015 IEEE Trustcom/BigDataSE/ISPA · doi:10.1109/trustcom.2015.357 · Cited by 724 · see citing works
Recent Advances in Extrusion‐Based 3D Printing for Biomedical Applications
Placone, J. K., & Engler, A. J. (2017) · Advanced Healthcare Materials · doi:10.1002/adhm.201701161 · Cited by 489 · see citing works
A taxonomy of computer program security flaws
Landwehr, C. E., Bull, A. R., McDermott, J. P., & Choi, W. S. (1994) · ACM Computing Surveys · doi:10.1145/185403.185412 · Cited by 451 · see citing works
Manufacturing and Security Challenges in 3D Printing
Zeltmann, S. E., Gupta, N., Tsoutsos, N. G., Maniatakos, M., Rajendran, J., & Karri, R. (2016) · JOM · doi:10.1007/s11837-016-1937-7 · Cited by 245 · see citing works
Self-citationCybersecurity for digital manufacturing
Wu, D., Ren, A., Zhang, W., Fan, F., Liu, P., Fu, X., & Terpenny, J. P. (2018) · Journal of Manufacturing Systems · doi:10.1016/j.jmsy.2018.03.006 · Cited by 160 · see citing works
Security analysis of the diebold AccuVote-TS voting machine
Feldman, A. J., Halderman, J. A., & Felten, E. W. (2007) · Cited by 152 · see citing works
Additive Manufacturing Cyber-Physical System: Supply Chain Cybersecurity and Risks
Gupta, N., Tiwari, A., Bukkapatnam, S. T. S., & Karri, R. (2020) · IEEE Access · doi:10.1109/access.2020.2978815 · Cited by 144 · cited 1× · see citing works
“The two major motivations for an attack on an AM CPS are [5]: 1) IP theft via product reverse engineering and/or counterfeiting, and 2) sabotage of either the printed part or the 3-D printer producing them.”
BackgroundSelf-citationA Review of Industry 4.0 Manufacturing Process Security Risks
Prinsloo, J., Sinha, S., & von Solms, B. (2019) · Applied Sciences · doi:10.3390/app9235105 · Cited by 140 · cited 1× · see citing works
“Prinsloo et al. [14] Survey Security risks within the Industry 4.0 manufacturing domain.”
InfluentialAM and aerospace: an ideal combination
Nickels, L. (2015) · Metal Powder Report · doi:10.1016/j.mprp.2015.06.005 · Cited by 116 · see citing works
Yampolskiy, M., Anthony Skjellum, Y., Kretzschmar, M., Overfelt, R. A., Sloan, K. R., & Yasinsac, A. (2016) · International Journal of Critical Infrastructure Protection · doi:10.1016/j.ijcip.2015.12.004 · Cited by 94 · see citing works
How Secure Are Printed Circuit Boards Against Trojan Attacks?
Ghosh, S., Basak, A., & Bhunia, S. (2014) · IEEE Design and Test · doi:10.1109/mdat.2014.2347918 · Cited by 79 · see citing works
Implications of Malicious 3D Printer Firmware
Moore, S., Glisson, W., & Yampolskiy, M. (2017) · Hawaii International Conference on System Sciences · doi:10.24251/hicss.2017.735 · Cited by 76 · see citing works
A Survey of Cybersecurity of Digital Manufacturing
Mahesh, P., Tiwari, A., Jin, C., Kumar, P. R., Reddy, A. L. N., Bukkapatnam, S., Gupta, N., & Karri, R. (2020) · Proceedings of the IEEE · doi:10.1109/jproc.2020.3032074 · Cited by 76 · see citing works
Self-citationTawk, C., Zhou, H., Sarıyıldız, E., Panhuis, M. I. H., Spinks, G. M., & Alıcı, G. (2020) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2020.3009365 · Cited by 73 · see citing works
A language for describing attacks on cyber-physical systems
Yampolskiy, M., Horváth, P., Koutsoukos, X., Xue, Y., & Sztipanovits, J. (2014) · International Journal of Critical Infrastructure Protection · doi:10.1016/j.ijcip.2014.09.003 · Cited by 60 · see citing works
Vulnerability analysis of desktop 3D printer software
Moore, S., Armstrong, P., McDonald, T., & Yampolskiy, M. (2016) · Resilience Week (RWS) · doi:10.1109/rweek.2016.7573305 · Cited by 48 · see citing works
Characteristic Aspects of Additive Manufacturing Security From Security Awareness Perspectives
Graves, L., Lubell, J., King, W. E., & Yampolskiy, M. (2019) · IEEE Access · doi:10.1109/access.2019.2931738 · Cited by 36 · see citing works
Novel Design and 3-D Printing of Nonassembly Controllable Pneumatic Robots
Wei, Y., Chen, Y., Yang, Y., & Li, Y. (2015) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2015.2492623 · Cited by 34 · see citing works
How to Ensure Bad Quality in Metal Additive Manufacturing
Slaughter, A., Yampolskiy, M., Matthews, M. J., King, W. E., Guss, G. M., & Elovici, Y. (2017) · International Conference on Availability, Reliability and Security (ARES) · doi:10.1145/3098954.3107011 · Cited by 32 · see citing works
fast16 as a Second-Order Subversion AttackPreprint
Bilar, D. Y. (2026) · doi:10.5281/zenodo.19901496 · Cited by 28 · see citing works
Robotized Additive Manufacturing of Funicular Architectural Geometries Based on Building Materials
Lakhal, O., Chettibi, T., Belarouci, A., Dherbomez, G., & Merzouki, R. (2020) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2020.2974057 · Cited by 24 · see citing works
Introduction to Hardware Trojans
Vosatka, J. (2017) · Springer eBooks · doi:10.1007/978-3-319-68511-3_2 · Cited by 23 · see citing works
Mac, G., Pearce, H. A., Karri, R., & Gupta, N. (2021) · Data in Brief · doi:10.1016/j.dib.2021.107286 · Cited by 11 · see citing works
Self-citation
Flagged first, then by citations
2 of the 27 references couldn’t be matched to a known paper.
Cited by
Sorted by citations
In-situ monitoring of sub-surface and internal defects in additive manufacturing: A review
AbouelNour, Y., & Gupta, N. (2022) · Materials & Design · doi:10.1016/j.matdes.2022.111063 · Cited by 193 · see citing works
Self-citationDifferential Evolution-Based Three Stage Dynamic Cyber-Attack of Cyber-Physical Power Systems
Lu, K., Wu, Z., & Huang, T. (2022) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2022.3214314 · Cited by 169 · see citing works
Wang, X., Hu, M., Luo, X., & Guan, X. (2024) · Electric Power Systems Research · doi:10.1016/j.epsr.2024.111126 · Cited by 42 · see citing works
Generative AI as a catalyst for HRM practices: mediating effects of trust
Prasad, K., & De, T. (2024) · Humanities and Social Sciences Communications · doi:10.1057/s41599-024-03842-4 · Cited by 81 · see citing works
Needle in a Haystack: Detecting Subtle Malicious Edits to Additive Manufacturing G-Code Files
Beckwith, C., Naicker, H. S., Mehta, S., Udupa, V. R., Nim, N. T., Gadre, V., Pearce, H. A., Mac, G., & Gupta, N. (2021) · IEEE Embedded Systems Letters · doi:10.1109/les.2021.3129108 · Cited by 24 · see citing works
Self-citationAhsan, M., Rais, M. H., & Ahmed, I. (2023) · IEEE European Symposium on Security and Privacy · doi:10.1109/eurosp57164.2023.00071 · Cited by 20 · see citing works
Kumar, M., Epiphaniou, G., & Maple, C. R. (2024) · Production Engineering · doi:10.1007/s11740-024-01283-1 · Cited by 19 · see citing works
Needle in a Haystack: Detecting Subtle Malicious Edits to Additive Manufacturing G-code Files
Beckwith, C., Sankar Naicker, H., Mehta, S., Udupa, V. R., Tri Nim, N., Gadre, V., Pearce, H. A., & Mac, G. (2021) · CUNY Academic Works (City University of New York) · Cited by 18 · see citing works
Self-citationLi, Z., Chen, X., Chen, Y., Li, S., Wang, H., Lv, S., & Sun, L. (2024) · IEEE Internet of Things Journal · doi:10.1109/jiot.2024.3358798 · Cited by 18 · see citing works
Yong, K., Chen, M., Liu, W., & Wu, Q. (2023) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2022.3229446 · Cited by 17 · see citing works
Deokar, S. U., Kumar, N., & Singh, R. P. (2025) · Results in Engineering · doi:10.1016/j.rineng.2025.104941 · Cited by 15 · see citing works
A Synergic Approach of Deep Learning towards Digital Additive Manufacturing: A Review
Pratap, A., Sardana, N., Utomo, S., Ayeelyan, J., Karthikeyan, P., & Hsiung, P. (2022) · Algorithms · doi:10.3390/a15120466 · Cited by 13 · see citing works
Alkofahi, H., Alawneh, H., & Anthony Skjellum, Y. (2024) · Computers & Security · doi:10.1016/j.cose.2024.103810 · Cited by 12 · see citing works
Cyberthreats and Security Measures in Drone-Assisted Agriculture
Tychola, K. A., & Rantos, K. (2025) · Electronics · doi:10.3390/electronics14010149 · Cited by 10 · see citing works
Kumar, M., Epiphaniou, G., & Maple, C. R. (2025) · Computers & Security · doi:10.1016/j.cose.2025.104557 · Cited by 9 · see citing works
Low-Magnitude Infill Structure Manipulation Attacks on Fused Filament Fabrication 3D Printers
Rais, M. H., Ahsan, M., Sharma, V., Barua, R., Prins, R., & Ahmed, I. (2022) · IFIP Advances in Information and Communication Technology · doi:10.1007/978-3-031-20137-0_8 · Cited by 9 · see citing works
Application of micro-computed tomography for authentication of 3D printed composite parts
Mac, G., Mandal, M., Rastogi, A., Gailani, G., Pearce, H. A., & Gupta, N. (2022) · Additive Manufacturing Letters · doi:10.1016/j.addlet.2022.100104 · Cited by 7 · see citing works
Self-citationMANIPULATION OF G-CODE TOOLPATH FILES IN 3D PRINTERS: ATTACKS AND MITIGATIONS
Kurkowski, E., Stockum, A. V., Dawson, J., Taylor, C. R., Schulz, T., & Shenoi, S. (2022) · IFIP advances in information and communication technology · doi:10.1007/978-3-031-20137-0_6 · Cited by 7 · see citing works
Scalable Security Enforcement for Cyber Physical Systems
Baird, A., Panda, A., Pearce, H. A., Pinisetty, S., & Roop, P. S. (2024) · IEEE Access · doi:10.1109/access.2024.3357714 · Cited by 6 · see citing works
Self-citationLayered Security Guidance for Data Asset Management in Additive Manufacturing
Milaat, F. A., & Lubell, J. (2023) · Journal of Computing and Information Science in Engineering · doi:10.1115/1.4064128 · Cited by 5 · see citing works
Real time 3D reconstruction for enhanced cybersecurity of additive manufacturing processes
Mishra, A. K., Goh, S. Y., Ganapathysubramanian, B., & Krishnamurthy, A. (2025) · Journal of Manufacturing Processes · doi:10.1016/j.jmapro.2025.04.004 · Cited by 5 · see citing works
Hu, W., Li, B., Wu, L., Li, Y., Li, X., & Hong, L. (2025) · IEEE Transactions on Dependable and Secure Computing · doi:10.1109/tdsc.2025.3604607 · Cited by 4 · see citing works
4D printing for energy storage systems: A transformative manufacturing paradigm
Zhaxybayeva, J., Anish, J., Muhammad, S., Carvalho, J. D. C., Singh, R., Dudar, N., & Chadha, U. (2026) · Journal of Energy Storage · doi:10.1016/j.est.2026.121542 · Cited by 5 · see citing works
Wang, X., Li, Y., Luo, X., & Guan, X. (2025) · International Journal of Electrical Power & Energy Systems · doi:10.1016/j.ijepes.2025.111156 · Cited by 4 · see citing works
On cyber sabotage risks in automated manufacturing of advanced composites
Mittal, S., Pearce, H. A., Yampolskiy, M., Oromiehie, E., & Prusty, B. G. (2025) · Additive Manufacturing Letters · doi:10.1016/j.addlet.2025.100280 · Cited by 3 · see citing works
Self-citationMachine learning-based early detection of malicious G-code manipulations in 3D printing
Ali, H. S., Cano, A., & Ahmed, I. (2025) · Journal of Manufacturing Processes · doi:10.1016/j.jmapro.2025.04.012 · Cited by 3 · see citing works
Induced alterations driven compromised structural properties in additively manufactured products
Haghnegahdar, L., Joshi, S. S., Venkata, R. Y., Riley, D. A., & Dahotre, N. B. (2024) · Rapid Prototyping Journal · doi:10.1108/rpj-07-2023-0236 · Cited by 3 · see citing works
Cyberattacks and Cybersecurity in Additive Manufacturing
Wang, L., Mosher, R. L., & Duett, P. (2024) · IEEE SoutheastCon · doi:10.1109/southeastcon52093.2024.10500033 · Cited by 3 · see citing works
Enhancing 3D Printing Infill Quality through Advanced Machine Learning
Wang, A., Wei, A.-T., Wang, H., & Chi, H. (2024) · International Conference on Electronics, Computers and Artificial Intelligence (ECAI) · doi:10.1109/ecai61503.2024.10607535 · Cited by 3 · see citing works
Rais, M. H., Ahsan, M., & Ahmed, I. (2022) · ACM Transactions on Cyber-Physical Systems · doi:10.1145/3704735 · Cited by 3 · see citing works
Blocklove, J., Raz, M., Roy, P. B., Pearce, H. A., Krishnamurthy, P., Khorrami, F., & Karri, R. (2024) · International Conference on Dependable Systems & Networks/Proceedings · doi:10.1109/dsn58291.2024.00057 · Cited by 2 · see citing works
Self-citationCleeman, J., Jackson, A., Patel, A., Wang, Z., Feldhausen, T. A., Shao, C., Xu, H., & Malhotra, R. (2025) · Journal of Manufacturing Systems · doi:10.1016/j.jmsy.2025.10.009 · Cited by 2 · see citing works
Machine learning recovers corrupted pharmaceutical 3D printing formulation data
Uddin, O., Mohammed, Y. A., Gaisford, S., & Elbadawi, M. (2025) · International Journal of Pharmaceutics · doi:10.1016/j.ijpharm.2025.126403 · Cited by 2 · see citing works
PowerGuard: Using Power Side-Channel Signals to Secure Motion Controllers in ICS
Li, S., Chen, Y., Chen, X., Li, Z., Fang, D., Liu, K., Lv, S., & Sun, L. (2024) · IEEE Transactions on Information Forensics and Security · doi:10.1109/tifs.2024.3451362 · Cited by 2 · see citing works
ATTACK-DEFENSE MODELING OF MATERIAL EXTRUSION ADDITIVE MANUFACTURING SYSTEMS
Stockum, A. V., Kurkowski, E., Potok, T., Taylor, C. R., Dawson, J., Rice, M., & Shenoi, S. (2022) · IFIP advances in information and communication technology · doi:10.1007/978-3-031-20137-0_5 · Cited by 2 · see citing works
Kurkowski, E., Rice, M., & Shenoi, S. (2022) · IFIP advances in information and communication technology · doi:10.1007/978-3-031-20137-0_7 · Cited by 2 · see citing works
An End-to-End Framework for Verifying and Validating Manufacturing Design Integrity
Jablonski, M., Everett, K., Ciocarlie, G. F., Đurić, Z., Hathhorn, C., Kimmell, J., Orlyanchik, V., Prevost, J. J., Robertson, G., Taylor, C., et al. (2025) · IFIP advances in information and communication technology · doi:10.1007/978-3-031-81888-2_5 · Cited by 1 · see citing works
AVOID: Automated Void Detection in STL Files
Roscoe, S., Hellbusch, L., Gunawardena, C., Deogun, J. S., Srisa‐an, W., Qian, Y., & Ciocarlie, G. F. (2025) · IEEE Transactions on Dependable and Secure Computing · doi:10.1109/tdsc.2025.3573652 · Cited by 1 · see citing works
3D Bioprinter Firmware Attacks: Categorization, Implementation, and Impacts
Ahsan, M., Najarro-Blancas, B., Ebode, J. T., Lewinski, N. A., & Ahmed, I. (2025) · IEEE International Symposium on Hardware Oriented Security and Trust (HOST) · doi:10.1109/host64725.2025.11050047 · Cited by 1 · see citing works
Monitoring energy consumption for cyberattack detection in additive manufacturing systems
Truong, X.-P., Jeon, H., Wang, Y., & Hong, S. H. (2025) · The International Journal of Advanced Manufacturing Technology · doi:10.1007/s00170-025-16551-2 · Cited by 1 · see citing works
Ahsan, M., Pak, E., Jackson, K., Rais, M. H., Najarro-Blancas, B., Lewinski, N. A., & Ahmed, I. (2024) · Annual Computer Security Applications Conference · doi:10.1109/acsac63791.2024.00036 · Cited by 1 · see citing works
Firewall3D: A Hardware Firewall for Defending 3D Printers Against Firmware Attacks
Asgar, S. A. G., & Reddy, N. (2026) · arXiv · doi:10.48550/arxiv.2607.10484
“Specifically, some regions of the printed object receive more filament, making them thicker, while other regions receive less, resulting in thinner sections[28,27,9,24].”
2022 Index IEEE-ASME Transactions on Mechatronics Vol. 27
(2022) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2022.3231757
Cyber-Attack Vectors Focused on Additive Manufacturing
Šlajs, T., Klaban, I., & Františ, P. (2023) · Communication and Information Technologies (KIT) · doi:10.1109/kit59097.2023.10297115
Chithras, T., Brijesh, K. J., Paul, M. M. R., Karthick, S., Bhuvanesh, A., & Keerthanadevi, R. (2024) · IEEE International Women in Engineering (WIE) Conference on Electrical and Computer Engineering (WIECON-ECE) · doi:10.1109/wiecon-ece64149.2024.10915180
Current Limitations and Future Directions
Gupta, N., & Beckwith, C. (2025) · Springer eBooks · doi:10.1007/978-3-031-98330-6_6
Self-citationLi, Z., Fang, D., Chen, Y., Li, S., Peng, J., Song, Z., Lv, S., & Sun, L. (2025) · ACM Transactions on Software Engineering and Methodology · doi:10.1145/3771764
Mamun, A. A., Kuzlu, M., Jovanović, V., & Sealy, W. (2025) · The International Journal of Advanced Manufacturing Technology · doi:10.1007/s00170-025-16795-y
AI assisted mechanical and performance testing of lightweight composites
Gupta, N., & Chen, G.-L. (2025) · Elsevier eBooks · doi:10.1016/b978-0-443-18852-7.00008-7
Self-citationKumar, M., Epiphaniou, G., & Maple, C. (2025) · SSRN Electronic Journal · doi:10.2139/ssrn.5477707
Nguyen, H. L., Feng, Z., Yuan, H. B., & Xu, H. (2026) · SSRN Electronic Journal · doi:10.2139/ssrn.6098689
Firmware, Dependability, and Trust
Michael, J. B. (2026) · Computer · doi:10.1109/mc.2025.3650406
QuietPrint: Protecting 3D Printers Against Acoustic Side-Channel Attacks
Ghazi Asgar, S. A., & Reddy, N. (2026) · Proceedings of the 12th ACM Cyber-Physical System Security Workshop · doi:10.1145/3775042.3807880
SCREAM: Secure Channels for Real-time Evaluation of Additive Manufacturing
Basu Roy, P., Blocklove, J., Bhargava, M., Pearce, H., Krishnamurthy, P., Sinanoglu, O., Gupta, N., Khorrami, F., & Karri, R. (2026) · Proceedings of the ACM Asia Conference on Computer and Communications Security · doi:10.1145/3779208.3805981
Self-citationNovel Digital Twins for Stoppage-free Operational Recovery from Stealthy Cyberphysical Attacks
Cleeman, J., Patel, A., Jackson, A., Wang, Z., Xu, L., Xu, H., & Malhotra, R. (2026) · Procedia CIRP · doi:10.1016/j.procir.2026.03.230
Khan, L., Mahmood, M. A., Sparks, T. E., & Liou, F. (2026) · Applied Sciences · doi:10.3390/app162010367
- Authors
- Pearce, H., Yanamandra, K., Gupta, N., & Karri, R.
- Affiliations
- New York University (US)
- Department of Mechanical and Aerospace Engineering and Center for Cybersecurity, New York University, New York, NY, USA
- Venue
- IEEE/ASME Transactions on Mechatronics
- Published
- 2022-12
- Volume
- 27
- Issue
- 6
- Pages
- 5361-5370
- ISSN
- 1083-4435 (ISSN-L)
- 1941-014X
- OpenAlex
- W3152917068
- Cited by
- 55
- References
- 27
- Citations by year
- 2026: 7 · 2025: 19 · 2024: 13 · 2023: 4 · 2022: 10 · 2021: 2
- FWCI
- 8.80
- Type
- journal article
- Language
- en
- Open access
- green
- arxiv.org
- Licence
- Locations
- IEEE/ASME Transactions on Mechatronics (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- arXiv (Cornell University)
- Funders
- National Science Foundation SaTC-EDU (DGE-1931724)
- Topics
- Physical Sciences › Computer Science › Hardware and Architecture › Physical Unclonable Functions (PUFs) and Hardware Security
- Physical Sciences › Computer Science › Artificial Intelligence › Security and Verification in Computing
- Physical Sciences › Engineering › Automotive Engineering › Additive Manufacturing and 3D Printing Technologies
- Keywords
- additive manufacturing, bootloader, Marlin firmware, AVR microcontroller, hardware security, tensile strength, print quality, cyber-physical attacks
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review