The DOI matches its Crossref record; 55 of the 55 references it cites were found in a registry or an index.
Adaptive Identification of Nonlinear Friction and Load Torque for PMSM Drives via a Parallel-Observer-Based Network With Model Compensation
Abstract
Acquiring the accurate knowledge of nonlinear friction and load torque is of great interest for optimizing the control behavior of permanent-magnet synchronous motor drives. In this work, a friction-and-load adaptive identification scheme based on a parallel-observer-based network with model compensation (POBN-MC) is presented. The developed network possesses a parallel structure consisting of the designed two novel observers, which involve a gain-adaptation super-twisting load torque observer and a variable-learning-rate Adaline inertia observer. A nonempirical friction model is proposed to capture friction, forming the model compensation part that is exploited for correcting the torque input of the network. With a two-step mechanism derived from the POBN-MC, the proposed scheme attains the online adaptive identification of the friction and load torque in a manner that integrates both accuracy and simplicity. In the first step, an explicit mapping relationship between the nonlinear friction torque and the rotor speed is determined with the speed response triggered by the natural deceleration. The second step accomplishes the online observation with regard to friction-and-load information matching the real-time operating conditions. Sufficient theoretical analyses, as well as the validations of numerous simulations and experiments, are presented to support the suggested scheme.
Overview
Integrity signals
Registry
Cites
Statistics
Verification
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?
Coupled inductor technology applied to bidirectional Cuk converters significantly minimizes the impact of current ripple while improving overall EMI performance.
“This innovation was later successfully applied to bidirectional ´ Cuk converters, which significantly minimizes the impact of current ripple while improving overall EMI performance [46].”
From Bidirectional DC-DC Converter Topologies for Hybrid Energy Storage Systems in Electric Vehicles: A Comprehensive Review (2025) · cites this paper as [46]
Citations
Cites
Motion control for advanced mechatronics
Ohnishi, K., Shibata, M., & Murakami, T. (1996) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/3516.491410 · Cited by 1,882
A Lyapunov approach to second-order sliding mode controllers and observers
Moreno, J. A., & Osorio, M. (2008) · Proceedings of the IEEE Conference on Decision & Control, including the Symposium on Adaptive Processes · doi:10.1109/cdc.2008.4739356 · Cited by 1,021
Speed Control for PMSM Servo System Using Predictive Functional Control and Extended State Observer
Liu, H., & Li, S. (2011) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2011.2162217 · Cited by 775
A High-Speed Sliding-Mode Observer for the Sensorless Speed Control of a PMSM
Kim, H., Son, J., & Lee, J.-M. (2010) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2010.2098357 · Cited by 736
Zhang, X., Sun, L., Zhao, K., & Sun, L. Z. (2012) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2012.2206610 · Cited by 727
Disturbance/Uncertainty Estimation and Attenuation Techniques in PMSM Drives—A Survey
Yang, J., Chen, W., Li, S., Guo, L., & Yan, Y. (2016) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2016.2583412 · Cited by 699
Design and Implementation of Terminal Sliding Mode Control Method for PMSM Speed Regulation System
Li, S., Zhou, M., & Yu, X. (2012) · IEEE Transactions on Industrial Informatics · doi:10.1109/tii.2012.2226896 · Cited by 507
Robust motion controller design for high-accuracy positioning systems
Lee, H., & Tomizuka, M. (1996) · IEEE Transactions on Industrial Electronics · doi:10.1109/41.481407 · Cited by 436
A New Reaching Law for Antidisturbance Sliding-Mode Control of PMSM Speed Regulation System
Wang, Y., Feng, Y., Zhang, X., & Liang, J. (2019) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2019.2933613 · Cited by 421
Adaptive Speed Control of PMSM Drive System Based a New Sliding-Mode Reaching Law
Junejo, A. K., Xu, W., Mu, C., Ismail, M. M., & Liu, Y. (2020) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2020.2986893 · Cited by 381
Wang, Y., Gu, L., Xu, Y., & Cao, X. (2016) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2016.2569454 · Cited by 356
ADALINE-Network-Based PLL for Position Sensorless Interior Permanent Magnet Synchronous Motor Drives
Zhang, G., Wang, G., Xu, D., & Zhao, N. (2015) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2015.2424256 · Cited by 324
Feng, Y., Yu, X., & Han, F. (2012) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2012.2213561 · Cited by 273
Sliding-Mode Observer-Based Mechanical Parameter Estimation for Permanent Magnet Synchronous Motor
Zhang, X., & Li, Z. (2015) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2015.2495183 · Cited by 227
Fuzzy Sliding Mode Speed Controller for PM Synchronous Motors With a Load Torque Observer
Leu, V. Q., Choi, H. H., & Jung, J. (2011) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2011.2161488 · Cited by 201
Precision Control and Compensation of Servomotors and Machine Tools via the Disturbance Observer
Huang, W.-S., Liu, C.-W., Hsu, P., & Yeh, S. (2009) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2009.2034178 · Cited by 158
Wang, Q.-K., He, Y.-J., Shen, J.-N., Hu, X.-S., & Ma, Z.-F. (2018) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2017.2780184 · Cited by 146
Sun, X., Wu, J., Lei, G., Guo, Y. G., & Zhu, J. G. (2020) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2020.3020026 · Cited by 141
Lian, C., Xiao, F., Gao, S., & Liu, J. (2018) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2018.2870078 · Cited by 137
Moment of Inertia and Friction Torque Coefficient Identification in a Servo Drive System
Kim, S. (2018) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2018.2826456 · Cited by 119
Load Torque Estimation and Passivity-Based Control of a Boost-Converter/DC-Motor Combination
Flores, J. L., Reger, J., & Sira-Ramirez, H. J. (2010) · IEEE Transactions on Control Systems Technology · doi:10.1109/tcst.2009.2037809 · Cited by 117
A measurement procedure for viscous and coulomb friction
Kelly, R., Llamas, J.-D., & Campa, R. (2000) · IEEE Transactions on Instrumentation and Measurement · doi:10.1109/19.863938 · Cited by 116
Ammar, A., Bourek, A., & Benakcha, A. (2017) · ISA Transactions · doi:10.1016/j.isatra.2017.01.010 · Cited by 115
Adaptive Sliding Mode Observer-Based Sensorless Control for SPMSM Employing a Dual-PLL
Chen, Z., Dawara, A. A., Zhang, X., Zhang, H., Liu, C., & Luo, G. (2021) · IEEE Transactions on Transportation Electrification · doi:10.1109/tte.2021.3112123 · Cited by 109
On-line Inertia Identification Algorithm for PI Parameters Optimization in Speed Loop
Niu, L., Xu, D., Yang, M., Gui, X., & Liu, Z. (2014) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2014.2307061 · Cited by 95
Wang, B., Luo, C., Yu, Y. H., Wang, G., & Xu, D. (2017) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2017.2765522 · Cited by 87
Robust speed-controlled induction-motordrive usingEKF and RLS estimators
Lin, F. (1996) · IEE Proceedings - Electric Power Applications · doi:10.1049/ip-epa:19960287 · Cited by 72
Lu, W., Zhang, Z., Wang, D., Lu, K., Wu, D., Ji, K., & Liang, G. L. (2018) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2018.2881217 · Cited by 68
Gong, C., Hu, Y., Ni, K., Liu, J., & Gao, J. (2019) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2019.2929714 · Cited by 63
Yang, C., Song, B., Xie, Y., & Tang, X. (2021) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2021.3067328 · Cited by 61
Robust and Stable Disturbance Observer of Servo System for Low-Speed Operation
Lee, K., & Blaabjerg, F. (2007) · IEEE Transactions on Industry Applications · doi:10.1109/tia.2007.895704 · Cited by 54
Zuo, Y., Mei, J., Zhang, X., & Lee, C. H. T. (2020) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2020.3000656 · Cited by 46
Bai, Y. R., Zhang, G., Wang, Q., Ding, D., Li, B., Wang, G., & Xu, D. (2022) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2022.3180348 · Cited by 44
Identification and control of electro-mechanical systems using state-dependent parameter estimation
Janot, A., Young, P. C., & Gautier, M. (2016) · International Journal of Control · doi:10.1080/00207179.2016.1209565 · Cited by 41
Modified Gbest-guided artificial bee colony algorithm with new probability model
Cui, L., Zhang, K., Li, G., Fu, X., Wen, Z., Lu, N., & Lu, J. J. (2017) · Soft Computing · doi:10.1007/s00500-017-2485-y · Cited by 38
A novel inertia identification method for speed control of electric machine
Hong, S., Kim, H.-W., & Sul, S. (1996) · Proceedings of the Annual Conference of the IEEE Industrial Electronics Society · doi:10.1109/iecon.1996.566056 · Cited by 37
Design of Speed Control Loop of A Variable Speed Diesel Engine Generator by Electric Governor
Lee, S., Yim, J.-S., Lee, J., & Sul, S. (2008) · IEEE Industry Applications Society Annual Meeting (IAS) · doi:10.1109/08ias.2008.202 · Cited by 36
Zhu, X., Zhang, H., Yang, B., & Zhang, G. (2017) · Mechanical Systems and Signal Processing · doi:10.1016/j.ymssp.2017.07.006 · Cited by 35
Yao, Y. H., Huang, Y., Peng, F., Dong, J., & Zhu, Z. (2021) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2021.3106510 · Cited by 32
Yang, C., Song, B., Xie, Y., Lu, S., & Tang, X. (2022) · IEEE Journal of Emerging and Selected Topics in Power Electronics · doi:10.1109/jestpe.2021.3111122 · Cited by 29
Amin, M. M. N., El-Sousy, F. F. M., Mohammed, O. A., Aziz, G. A. A., & Gaber, K. (2021) · IEEE Transactions on Industry Applications · doi:10.1109/tia.2021.3115088 · Cited by 28
A Novel Sensitivity Analysis to Moment of Inertia and Load Variations for PMSM Drives
Tarczewski, T., Szczepański, R., Erwiński, K., Hu, X., & Grzesiak, L. M. (2022) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2022.3188404 · Cited by 28
Dynamic model based auto-tuning digital servo driver
Kobayashi, S., Awaya, I., Kuromaru, H., & Oshitani, K. (1995) · IEEE Transactions on Industrial Electronics · doi:10.1109/41.464608 · Cited by 27
Yang, C., Song, B., Xie, Y., Lu, S., & Tang, X. (2022) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2022.3161760 · Cited by 25
Adaptive load observer-based feed-forward control in PMSM drive system
Zhao, S., Chen, Y., & Mao, Y. (2014) · Transactions of the Institute of Measurement and Control · doi:10.1177/0142331214541139 · Cited by 24
Adaptive disturbance compensation and load torque estimation for speed control of a servomechanism
Chen, C.-Y., & Cheng, M.-Y. (2012) · International Journal of Machine Tools and Manufacture · doi:10.1016/j.ijmachtools.2012.03.006 · Cited by 23
Estimations of load parameters for PMSM by MRAS
Wang, S., & Wan, S. (2011) · International Conference on Electrical and Control Engineering · doi:10.1109/iceceng.2011.6057560 · Cited by 22
Fireworks explosion based artificial bee colony for numerical optimization
Chen, X., Wei, X., Yang, G., & Du, W. (2019) · Knowledge-Based Systems · doi:10.1016/j.knosys.2019.105002 · Cited by 20
Kim, H., Kim, H., & Choi, J. (2019) · IET Electric Power Applications · doi:10.1049/iet-epa.2019.0643 · Cited by 20
Identification of mechanical parameters in servo-drive system
Szczepański, R., Tarczewski, T., Niewiara, L. J., & Stojić, D. M. (2021) · International Power Electronics and Motion Control Conference (EPE-PEMC) · doi:10.1109/pemc48073.2021.9432595 · Cited by 15
Tarczewski, T., Niewiara, L. J., & Grzesiak, L. M. (2020) · Bulletin of the Polish Academy of Sciences Technical Sciences · doi:10.24425/bpasts.2020.134649 · Cited by 14
Friction and disturbance compensation for speed control of servo control systems
Wu, J.-C., Su, K.-H., & Cheng, M.-Y. (2010) · Proceedings of the Annual Conference of the IEEE Industrial Electronics Society · doi:10.1109/iecon.2010.5675379 · Cited by 6
Sliding mode control with friction observer and load observer of PMSM
Chai, L., & Yao, F. (2015) · International Conference on Control, Automation and Systems (ICCAS) · doi:10.1109/iccas.2015.7364784 · Cited by 5
Niewiara, L. J., Tarczewski, T., & Grzesiak, L. M. (2019) · European Conference on Power Electronics and Applications · doi:10.23919/epe.2019.8914782 · Cited by 4
Comparison of Online Inertia Identification Methods for Permanent Magnet Synchronous Motor
Liu, T., Ye, Z., & Griepentrog, G. (2019) · Cited by 3
Flagged first, then by citations
Cited by
Sorted by citations
Tong, Y., Salhi, I., Wang, Q., Lu, G., & Wu, S. (2025) · Energies · doi:10.3390/en18092312 · Cited by 60
“This innovation was later successfully applied to bidirectional ´Cuk converters, which significantly minimizes the impact of current ripple while improving overall EMI performance [46].”
Wang, W., Ye, Y., Chen, X., & Yuan, Y. (2025) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2025.3559890 · Cited by 26
Safety Management Technologies for Wireless Electric Vehicle Charging Systems: A Review
Niu, S., Jia, Q., Yang, H., Yang, C., & Jian, L. (2025) · Electronics · doi:10.3390/electronics14122380 · Cited by 24
A novel multi-pulse friction compensation strategy for hybrid robots
Han, J., Cheng, H., Shan, X., Liu, H., Xiao, J., & Huang, T. (2024) · Mechanism and Machine Theory · doi:10.1016/j.mechmachtheory.2024.105726 · Cited by 17
Chang, H., Lu, S., Huang, G., Zheng, S., & Song, B. (2023) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2023.3303371 · Cited by 16
Tang, S., Cao, Y., Shi, T., Yan, Y., & Xia, C. (2024) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2024.3509863 · Cited by 16
Parameter-Tuning-Free Two-Step Identification of Mechanical Parameters for PMSM Drives
Yang, C., Liu, W., Niu, S., Lyu, J., & Chau, K. T. (2025) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2025.3577312 · Cited by 14
Zhang, C., Zhang, L., Wang, D., & Lu, K. (2023) · International Journal of Electrical Power & Energy Systems · doi:10.1016/j.ijepes.2023.109666 · Cited by 13
Luan, M., Ruan, J., Zhang, Y., Yan, H., & Wang, L. (2024) · Actuators · doi:10.3390/act13100395 · Cited by 11
Duan, Y., Gao, C., Xu, Z., Ren, S., & Wu, D. (2025) · Energies · doi:10.3390/en18092283 · Cited by 11
Yang, C., Song, B., Jatskevich, J., Zhang, H., & Lee, C. H. T. (2024) · IEEE Transactions on Industrial Informatics · doi:10.1109/tii.2023.3345471 · Cited by 9
Li, J., Chen, Z., Hu, H., Liu, X., & Guo, Y. G. (2024) · IEEE Transactions on Industry Applications · doi:10.1109/tia.2024.3457953 · Cited by 8
Stable Inertia Identification Considering Precise Cogging Torque Under Low-Speed Operation
Chang, H., Lu, S., Song, B., & Yang, J. (2024) · IEEE Transactions on Industrial Electronics · doi:10.1109/tie.2024.3456901 · Cited by 7
Chang, H., Wang, Z., Yang, J., Li, S., & Lu, S. (2025) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2025.3560352 · Cited by 7
Tian, S., Liu, K., Zhang, M., Lu, C., Wu, M., & She, J. (2024) · IEEE/ASME Transactions on Mechatronics · doi:10.1109/tmech.2024.3402651 · Cited by 7
Luan, M., Zhang, Y., Ruan, J., Guo, Y., Wang, L., & Min, H. (2024) · Actuators · doi:10.3390/act13120525 · Cited by 3
Controller Parameter Self-Commissioning Scheme for Speed Sensorless Induction Motor Drives
Zhao, K., Song, B., Tang, X., Zhou, X., & Yang, C. (2025) · IEEE Transactions on Energy Conversion · doi:10.1109/tec.2025.3561321 · Cited by 2
Wu, S., Ren, W., Tong, C., Yang, S., & Zheng, P. (2025) · IEEE Journal of Emerging and Selected Topics in Power Electronics · doi:10.1109/jestpe.2025.3609935 · Cited by 2
Guo, L., Zhou, G., Song, N., Zhu, M., & Mu, Y. (2023) · IEEE Access · doi:10.1109/access.2023.3347590 · Cited by 2
A DRL-Based Edge Intelligent Servo Control with Semi-closed-Loop Feedbacks in Industrial IoT
Zheng, H., Zhu, H., Wu, H. B., Yi, C., Zhu, K., & Dai, X. (2024) · Lecture notes in computer science · doi:10.1007/978-3-031-71467-2_33 · Cited by 2
Health monitoring of planetary gearbox using motor’s control signals
Chen, D., Zhao, M. J., Han, X., Li, S., & Zhang, Y. (2025) · Journal of Sound and Vibration · doi:10.1016/j.jsv.2025.119332 · Cited by 2
Yau, H., Chen, Y.-T., & Lin, P.-L. (2026) · IEEE Transactions on Automation Science and Engineering · doi:10.1109/tase.2026.3667105 · Cited by 1
Finite-time sliding mode speed control using an adaptive three-stage reaching law for PMSM
Huang, Y., Lu, S., Song, B., & Zheng, S. (2026) · ISA Transactions · doi:10.1016/j.isatra.2026.06.010 · Cited by 1
Load Torque Observer for BLDC Motors Based on a HOSM Differentiator
Coronado-Andrade, A., de la Guerra, A., & Álvarez-Icaza, L. A. (2023) · Machines · doi:10.3390/machines11121065 · Cited by 1
Control Strategy of Transmission Mechanism Based on Load Torque Feedforward Strategy
Xu, H., Xiao, X., Song, Z., & Liu, Z. (2024) · IEEE International Conference on Electrical Energy Conversion Systems and Control (IEECSC) · doi:10.1109/ieecsc62814.2024.10913965 · Cited by 1
Liu, L., Huang, Z., Liu, Z., Tian, L., Liu, Z., & Xiao, W. (2025) · Lecture notes in electrical engineering · doi:10.1007/978-981-96-1395-3_13
Motion Intensity Evaluation Algorithm Under Fuzzy Observer
Li, Y., & Liu, K. (2025) · Lecture notes in electrical engineering · doi:10.1007/978-981-96-2794-3_31
PDF Control for Rotation-Modulating RLG INS
Zhang, P., Lei, H., Chen, P., & Li, W. (2025) · Lecture notes in electrical engineering · doi:10.1007/978-981-96-2248-1_49
Wang, S., Li, B., Zhang, G., Wang, G., Chen, J., Yu, J., & Xu, D. (2025) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2025.3588522
A Sensorless Control Strategy for PMSM Based on ALST-SMO
Chen, D., Shi, J., Xiao, Z., & Yang, K. (2024) · International Conference on Mechatronics and Computer Technology Engineering (MCTE) · doi:10.1109/mcte62870.2024.11117340
Chen, Q., Tang, L., Zhang, W., Li, Z., Lin, T., & Ren, H. (2025) · IET Power Electronics · doi:10.1049/pel2.70142
Yang, K., Lu, Y., Li, X., & Feng, G. (2025) · IEEE Journal of Emerging and Selected Topics in Power Electronics · doi:10.1109/jestpe.2025.3640393
An, Q., Ni, F., & Bian, C. (2025) · IEEE China International Youth Conference on Electrical Engineering (CIYCEE) · doi:10.1109/ciycee67631.2025.11308795
Sensorless Control of DTP-PMSM Based on an Improved Sliding Mode Observer
Xiao, S., Bu, W., Zhang, X., & Gao, Y. (2025) · IEEE International Conference on Civil Aviation Safety and Information Technology (ICCASIT) · doi:10.1109/iccasit66611.2025.11348728
Wang, X., Lu, S., Zheng, S., & Song, B. (2026) · IEEE Transactions on Power Electronics · doi:10.1109/tpel.2026.3682870
Han, T., Cheng, H., Wang, H., Wei, W., Feng, X., & Liu, S. (2026) · Aerospace Science and Technology · doi:10.1016/j.ast.2026.113314
Nominal sliding mode control of PMSM based on friction and disturbance compensation
Wang, T., Liu, W., Hu, H., Wang, H., Han, L., & Liu, Y. (2026) · Royal Society Open Science · doi:10.1098/rsos.252541
Metadata
- Authors
- Yang, C., Song, B., Xie, Y., Zheng, S., & Tang, X.
- Affiliations
- State Key Laboratory of Digital Manufacturing Equipment and Technology (CN)
- China University of Geosciences (CN)
- Venue
- IEEE Transactions on Power Electronics
- Published
- 2023-05
- Volume
- 38
- Issue
- 5
- Pages
- 5875-5897
- ISSN
- 0885-8993 (ISSN-L)
- 1941-0107
- OpenAlex
- W4317892504
- Cited by
- 37
- References
- 55
- Citations by year
- 2026: 5 · 2025: 17 · 2024: 11 · 2023: 4
- FWCI
- 2.75
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- Locations
- IEEE Transactions on Power Electronics (publishedVersion)
- Funders
- National Key R&D Program of China (2020YFB1711300)
- Key R&D Project of Hubei (2022BAA061)
- National Natural Science Foundation of China (52105019)
- Major Science and Technology Project of Guangdong (2020B090927001)
- Topics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Sensorless Control of Electric Motors
- Physical Sciences › Engineering › Mechanical Engineering › Control Systems in Engineering
- Physical Sciences › Engineering › Control and Systems Engineering › Adaptive Control of Nonlinear Systems
- Keywords
- load torque estimation, permanent magnet synchronous motor, super-twisting sliding mode observer, model compensation, online parameter estimation
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