Leveraging MTG-FCI fire observations for event-based fire behavior monitoring from near-real-time operation to seasonal analysis
Pith reviewed 2026-06-27 22:52 UTC · model grok-4.3
The pith
The Fire Event Tracker clusters MTG-FCI fire detections into persistent events using fixed spatio-temporal rules, delivering consistent updates on fire geometry, power, and spread every 10 minutes.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Event-based clustering of FCI active fire detections provides a consistent description of fire evolution. The FET algorithm performs spatio-temporal clustering on the LSA-SAF FCI active fire product, assigns persistent identifiers to fire events, and updates their geometry, fire radiative power, and rate of spread at each 10-min interval. The same parameterization supports both near-real-time operation and retrospective processing of the Mediterranean 2025 archive, as demonstrated in Portugal wildfire monitoring and the SILEX airborne campaign.
What carries the argument
The Fire Event Tracker (FET) algorithm, which performs spatio-temporal clustering of hotspot detections to assign persistent identifiers and update fire attributes at 10-minute intervals with one fixed parameterization.
Load-bearing premise
A single fixed set of spatio-temporal clustering rules can reliably link individual hotspot detections into coherent fire events across different fire sizes, observation conditions, and regions without frequent splitting or merging mistakes.
What would settle it
Systematic observation that the same fires fragment into multiple identifiers or that separate fires merge under the fixed rules when applied to fires of varying sizes or under different viewing angles and atmospheric conditions.
Figures
read the original abstract
Wildfire monitoring and suppression require timely information on fire behavior, including fire energy release and rate of spread, to support operational decision-making and resource allocation. Active fire products from the Flexible Combined Imager (FCI) aboard the geostationary Meteosat Third Generation (MTG) satellites provide 10-min observations over Europe and Africa. Deriving fire behavior information from these observations requires associating individual hotspot detections into coherent fire events. We present a Fire Event Tracker (FET) algorithm that performs spatio-temporal clustering of hotspot detections from the LSA-SAF FCI active fire product. The algorithm assigns persistent identifiers to fire events and updates their geometry, fire radiative power, and rate of spread at each 10-min interval. The same parameterization is used for both near-real-time and retrospective processing. FET was applied retrospectively to the Mediterranean FCI hotspot archive of 2025 and operationally in two near-real-time contexts: wildfire monitoring in Portugal and support of the 2025 SILEX airborne campaign within the EUBURN project, where besides fire monitoring, FET products were also used to initialize coupled FOREFIRE-MesoNH simulations for plume forecasting. Results show that event-based clustering of FCI active fire detections provides a consistent description of fire evolution, enabling both tactical wildfire management and high-frequency seasonal fire analyses.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents the Fire Event Tracker (FET) algorithm that performs spatio-temporal clustering of hotspot detections from the LSA-SAF FCI active fire product to associate individual detections into coherent fire events with persistent identifiers. The algorithm updates fire geometry, radiative power, and rate of spread at 10-min intervals using the same parameterization for near-real-time operations in Portugal, support of the SILEX campaign, and retrospective analysis of the 2025 Mediterranean archive. The central claim is that this approach provides a consistent description of fire evolution suitable for both tactical management and high-frequency seasonal analyses.
Significance. Should the algorithm's consistency be demonstrated through quantitative validation, this contribution would enable timely fire behavior monitoring from geostationary satellite data at 10-minute resolution, which has potential value for operational wildfire suppression and detailed studies of fire regimes over Europe and Africa.
major comments (2)
- [Abstract] The statement 'Results show that event-based clustering of FCI active fire detections provides a consistent description of fire evolution' is presented without any quantitative performance metrics, validation against independent data, error analysis, or comparison to baselines, which is load-bearing for the central claim of providing a consistent description across NRT and seasonal contexts.
- [Results] No diagnostics are reported to address the assumption that a single fixed parameterization of spatio-temporal clustering reliably groups hotspots without substantial fragmentation or erroneous merging across varying fire sizes, cloud cover, or regional conditions, such as event lifetime distributions or overlap with independent perimeters.
minor comments (1)
- The abstract is quite long and could be condensed for clarity while retaining key claims.
Simulated Author's Rebuttal
We thank the referee for the constructive review. The comments highlight the need for stronger quantitative support for the consistency claim, which we address below by proposing targeted revisions while noting limitations in available validation data.
read point-by-point responses
-
Referee: [Abstract] The statement 'Results show that event-based clustering of FCI active fire detections provides a consistent description of fire evolution' is presented without any quantitative performance metrics, validation against independent data, error analysis, or comparison to baselines, which is load-bearing for the central claim of providing a consistent description across NRT and seasonal contexts.
Authors: We agree the abstract phrasing overstates the evidential basis. The manuscript shows consistency via identical parameterization applied to NRT operations in Portugal, SILEX campaign support, and the full 2025 Mediterranean archive, with practical utility illustrated through those deployments. We will revise the abstract to remove the load-bearing claim and instead state that the approach enables consistent monitoring across contexts, supported by the operational examples. No formal error analysis or baseline comparisons exist in the current work. revision: yes
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Referee: [Results] No diagnostics are reported to address the assumption that a single fixed parameterization of spatio-temporal clustering reliably groups hotspots without substantial fragmentation or erroneous merging across varying fire sizes, cloud cover, or regional conditions, such as event lifetime distributions or overlap with independent perimeters.
Authors: The fixed parameterization is used uniformly across the reported applications, providing indirect support through successful event tracking in varied conditions. We will add event lifetime distributions and basic fragmentation/merging discussion drawn from the 2025 archive in a revised Results section. Overlap with independent perimeters is not feasible with data available to the authors. revision: partial
- Quantitative overlap analysis with independent fire perimeters to validate clustering accuracy
Circularity Check
No circularity: algorithmic pipeline with fixed parameters
full rationale
The paper presents the FET algorithm as a fixed-parameter spatio-temporal clustering method applied to FCI hotspot data. No equations derive a target quantity from fitted inputs, no predictions are made by construction from the same data used to set parameters, and no self-citation chain or uniqueness theorem is invoked to justify the central claim. The results are outcomes of running the described pipeline on independent archives and operational streams; the consistency claim is an empirical observation of the output rather than a tautological reduction to the inputs.
Axiom & Free-Parameter Ledger
free parameters (1)
- spatio-temporal clustering thresholds
axioms (1)
- domain assumption Individual hotspot detections from the LSA-SAF FCI product can be associated into coherent fire events via spatio-temporal clustering
Reference graph
Works this paper leans on
-
[1]
Denjean, Cyrielle and Pelletier, Sophie and Rodier, Quentin and Velazquez-Garcia, Alejandra and Libois, Quentin and Paugam, Ronan and Borbon, Agn. La M. doi:10.37053/LAMETEOROLOGIE-2025-0080 , issn =
-
[2]
Global Change Biology , month =
S. Global Change Biology , month =. doi:10.1111/GCB.70649 , file =
-
[3]
and Burton, Chantelle and Giuseppe, Francesca Di and Jones, Matthew W
Kelley, Douglas I. and Burton, Chantelle and Giuseppe, Francesca Di and Jones, Matthew W. and Barbosa, Maria L.F. and Brambleby, Esther and McNorton, Joe R. and Liu, Zhongwei and Bradley, Anna S.I. and Blackford, Katie and Burke, Eleanor and Ciavarella, Andrew and Tomaso, Enza Di and Eden, Jonathan and Ferreira, Igor Jos. Earth System Science Data , month...
-
[4]
Metsu, Christophe and Maes, Wouter H. and Ottoy, Sam and. Methods in Ecology and Evolution , keywords =. doi:10.1111/2041-210X.70196 , file =
-
[5]
Aurell, Johanna and Velanas, Pantelis and Gonz. Drones 2025, Vol. 9, Page 615 , keywords =. doi:10.3390/DRONES9090615 , file =
-
[6]
Hofmann, Martin and Zenz, David and Raposo, Jorge and Agueda, Alba and Planas, Eulalia and Pastor, Elsa , doi =
-
[7]
Paugam, Ronan and Benali, Akli and Harvie, Julia and Meraner, Andrea and Andela, Niels and Xu, Weidong , eprint =
-
[8]
and Prins, Elaine M
Koltunov, Alexander and Ustin, Susan L. and Prins, Elaine M. , doi =. Remote Sensing of Environment , keywords =
-
[9]
and Kaufman, Yoram J
Giglio, Louis and Descloitres, Jacques and Justice, Christopher O. and Kaufman, Yoram J. , doi =. Remote Sensing of Environment , keywords =
-
[10]
doi:10.1111/J.1365-2664.2010.01774.X , file =
Journal of Applied Ecology , keywords =. doi:10.1111/J.1365-2664.2010.01774.X , file =
-
[11]
Annual Review of Fluid Mechanics , month =
Banerjee, Tirtha , doi =. Annual Review of Fluid Mechanics , month =
-
[12]
Dekavalla, Maria and Paletta, Quentin and Tsiakos, Chrysovalantis and Amditis, Angelos , doi =
-
[13]
and Lakkis, Issam and Soteriou, Marios , doi =
Ghoniem, Ahmed F. and Lakkis, Issam and Soteriou, Marios , doi =. Symposium (International) on Combustion , month =
-
[14]
Sun, Jie and Speer, Kevin and Quaife, Bryan and Cai, Ming and Schvartzman, David , eprint =
-
[15]
Journal of Applied Meteorology and Climatology , number =
Haines, Donald A and Smith, Mahlon C , doi =. Journal of Applied Meteorology and Climatology , number =
-
[16]
Heilman, Warren E. , doi =. International Journal of Wildland Fire , keywords =
-
[17]
and McCabe, Tempest D
Coffield, Shane R. and McCabe, Tempest D. and Schroeder, Wilfrid and Chen, Yang and Scholten, Rebecca C. and Orland, Elijah and Liu, Tianjia and Wiggins, Elizabeth and Randerson, James T. and Follette-Cook, Melanie and Morton, Douglas C. , doi =. Remote Sensing of Environment , month =
-
[18]
Trigo, Isabel F. and Dacamara, Carlos C. and Viterbo, Pedro and Roujean, Jean Louis and Olesen, Folke and Barroso, Carla and Camacho-De-Coca, Fernando and Carrer, Dominique and Freitas, Sandra C. and Garc. International Journal of Remote Sensing , number =. doi:10.1080/01431161003743199 , issn =
-
[19]
and Justice, Christopher O
Kaufman, Yoram J. and Justice, Christopher O. and Flynn, Luke P. and Kendall, Jackie D. and Prins, Elaine M. and Giglio, Louis and Ward, Darold E. and Menzel, W. Paul and Setzer, Alberto W. , doi =. Journal of Geophysical Research: Atmospheres , keywords =
-
[20]
doi:10.5281/zenodo.10260790 , institution =
Chuvieco, Emilio and Yebra, Marta and Martino, Stefano and Thonicke, Kirsten and G. doi:10.5281/zenodo.10260790 , institution =
-
[21]
and Castellnou, M
Duane, A. and Castellnou, M. and Bachfisher, M. and Brotons, L. , doi =. JOURNAL OF ENVIRONMENTAL INFORMATICS , keywords =
-
[22]
and DaCamara, Carlos C
Pinto, Miguel M. and DaCamara, Carlos C. and Trigo, Isabel F. and Trigo, Ricardo M. and Turkman, K. Feridun , doi =. Natural Hazards and Earth System Sciences , month =
-
[23]
doi:10.2905/4BD142CE-1BAA-4A84-85C5-B5C676309D3A , howpublished =
-
[24]
International Journal of Disaster Risk Reduction , keywords =
Ascoli, Davide and Plana, Eduard and Oggioni, Silvio Daniele and Tomao, Antonio and Colonico, Mario and Corona, Piermaria and Giannino, Francesco and Moreno, Mauro and Xanthopoulos, Gavriil and Kaoukis, Konstantinos and Athanasiou, Miltiadis and Cola. International Journal of Disaster Risk Reduction , keywords =. doi:10.1016/j.ijdrr.2023.103715 , file =
-
[25]
Chuvieco, Emilio and Mouillot, Florent and van der Werf, Guido R. and. Remote Sensing of Environment , keywords =. doi:10.1016/J.RSE.2019.02.013 , file =
-
[26]
and Rochoux, M and Wooster, M , booktitle =
Paugam, R and Mell, W and Filippi, J.-B. and Rochoux, M and Wooster, M , booktitle =
-
[28]
Valabre , howpublished =
-
[29]
Wooster, M. J. and Xu, W. and Nightingale, T. , doi =. Remote Sensing of Environment , keywords =
-
[30]
Wooster, M. J. and Roberts, G. and Freeborn, P. H. and Xu, W. and Govaerts, Y. and Beeby, R. and He, J. and Lattanzio, A. and Fisher, D. and Mullen, R. , doi =. Atmospheric Chemistry and Physics , month =
-
[31]
Filippi, Jean Baptiste and Bosseur, Fr. Atmosphere , keywords =. doi:10.3390/ATMOS9060218 , file =
-
[32]
Paugam, Ronan and Gomex, Jorge and Benali, Akli , howpublished =
-
[33]
(EFFIS), European Forest Fire Information System , howpublished =
-
[34]
International Journal of Wildland Fire , keywords =
Su, Huiyi and Ma, Xiu and Li, Mingshi , doi =. International Journal of Wildland Fire , keywords =
-
[35]
Razu and Hassan, Quazi K
Dastour, Hatef and Bhuian, Hanif and Ahmed, M. Razu and Hassan, Quazi K. , doi =. Fire 2024, Vol. 7, Page 355 , keywords =
2024
-
[36]
and Amram, S
Mandel, J. and Amram, S. and Beezley, J. D. and Kelman, G. and Kochanski, A. K. and Kondratenko, V. Y. and Lynn, B. H. and Regev, B. and Vejmelka, M. , doi =. Natural Hazards and Earth System Sciences , month =
-
[37]
doi:10.1038/s41612-024-00575-8 , file =
npj Climate and Atmospheric Science 2024 7:1 , keywords =. doi:10.1038/s41612-024-00575-8 , file =
-
[38]
Jones, Matthew W. and Abatzoglou, John T. and Veraverbeke, Sander and Andela, Niels and Lasslop, Gitta and Forkel, Matthias and Smith, Adam J.P. and Burton, Chantelle and Betts, Richard A. and van der Werf, Guido R. and Sitch, Stephen and Canadell, Josep G. and Sant. Reviews of Geophysics , keywords =. doi:10.1029/2020RG000726 , file =
-
[39]
https://doi.org/10.1117/1.OE.62.3.035105 , keywords =
Leslie, Patrick and Grimming, Robert and Grijalva, Sarina and Butrimas, Steven and Driggers, Ronald , doi =. https://doi.org/10.1117/1.OE.62.3.035105 , keywords =
-
[40]
Mcnorton, Joe R. and. Biogeosciences , month =. doi:10.5194/BG-21-279-2024 , issn =
-
[41]
and Bernal, Alexis A
Stephens, Scott L. and Bernal, Alexis A. and Collins, Brandon M. and Finney, Mark A. and Lautenberger, Chris and Saah, David , doi =. Forest Ecology and Management , keywords =
-
[42]
and Qin, Yiren and Theodori, Maria and Zamanialaei, Maryam and Lautenberger, Chris and Trouv
Purnomo, Dwi M.J. and Qin, Yiren and Theodori, Maria and Zamanialaei, Maryam and Lautenberger, Chris and Trouv. Proceedings of the Combustion Institute , keywords =. doi:10.1016/J.PROCI.2024.105755 , file =
-
[43]
and Schroeder, Wilfrid and Chen, Yang and Brando, Paulo M
Andela, Niels and Morton, Douglas C. and Schroeder, Wilfrid and Chen, Yang and Brando, Paulo M. and Randerson, James T. , doi =. Science Advances , month =
-
[44]
Atmospheric Research , keywords =
Couto, Flavio Tiago and Filippi, Jean Baptiste and Baggio, Roberta and Campos, C. Atmospheric Research , keywords =. doi:10.1016/J.ATMOSRES.2024.107223 , file =
-
[45]
Ecological Modelling , keywords =
Cardil, Adri. Ecological Modelling , keywords =. doi:https://doi.org/10.1016/j.ecolmodel.2019.01.017 , file =
-
[46]
Andrews, Patricia L. , doi =. Gen. Tech. Rep. RMRS-GTR-266. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 39 p. , keywords =
-
[47]
and Veraverbeke, Sander and Chen, Yang and Randerson, James T
Scholten, Rebecca C. and Veraverbeke, Sander and Chen, Yang and Randerson, James T. , doi =. Nature Geoscience 2024 17:9 , keywords =
2024
-
[48]
Ecological Modelling , keywords =
Monedero, Santiago and Ramirez, Joaquin and Cardil, Adri. Ecological Modelling , keywords =. doi:10.1016/j.ecolmodel.2018.11.016 , file =
-
[49]
Scientific Data 2019 6:1 , keywords =
Art. Scientific Data 2019 6:1 , keywords =. doi:10.1038/s41597-019-0312-2 , file =
-
[50]
International Journal of Remote Sensing , keywords =
Humber, Michael and Zubkova, Maria and Giglio, Louis , doi =. International Journal of Remote Sensing , keywords =
-
[51]
https://doi.org/10.1139/x00-032 , month =
Jr, Ralph M Nelson , doi =. https://doi.org/10.1139/x00-032 , month =
-
[52]
Andrews, Patricia L. and Cruz, Miguel G. and Rothermel, Richard C. , doi =. International Journal of Wildland Fire. doi: http://dx.doi.org/10.1071/WF12122 , keywords =
-
[53]
and French, Jeffrey R
Kingsmill, David E. and French, Jeffrey R. and Lareau, Neil P. , doi =. Atmospheric Chemistry and Physics , month =
-
[54]
Engineering Applications of Artificial Intelligence , keywords =
Rub. Engineering Applications of Artificial Intelligence , keywords =. doi:10.1016/J.ENGAPPAI.2022.105649 , issn =
-
[55]
Fire Safety Journal , pages =
Zhou, Tengjiao and Ding, Long and Ji, Jie and Yu, Longxing and Wang, Zheng , doi =. Fire Safety Journal , pages =
-
[56]
Castellnou, Marc and Bachfischer, Mercedes and Miralles, Marta and Ruiz, Borja and Stoof, Cathelijne R. and. Journal of Geophysical Research: Atmospheres , keywords =. doi:10.1029/2022JD036920 , file =
-
[57]
Frontiers in Forests and Global Change , keywords =
Gonzalez-Olabarria, Jose Ramon and Carrasco, Jaime and Pais, Cristobal and Garcia-Gonzalo, Jordi and Palacios-Meneses, David and Mahaluf-Recasens, Rodrigo and Porkhum, Olena and Weintraub, Andr. Frontiers in Forests and Global Change , keywords =. doi:10.3389/FFGC.2023.1071484/BIBTEX , file =
-
[58]
IEEE Transactions on Geoscience and Remote Sensing , keywords =
Mazzeo, Giuseppe and Falconieri, Alfredo and Filizzola, Carolina and Genzano, Nicola and Pergola, Nicola and Marchese, Francesco , doi =. IEEE Transactions on Geoscience and Remote Sensing , keywords =
-
[59]
Owsley-Brown, Farrer and Wooster, Martin J and Grosvenor, Mark J and Liu, Yanan , doi =. Atmos. Meas. Tech , pages =
-
[60]
and Graff, Casey A
Chen, Yang and Hantson, Stijn and Andela, Niels and Coffield, Shane R. and Graff, Casey A. and Morton, Douglas C. and Ott, Lesley E. and Foufoula-Georgiou, Efi and Smyth, Padhraic and Goulden, Michael L. and Randerson, James T. , doi =. Scientific Data 2022 9:1 , keywords =
2022
-
[61]
Giglio, Louis and Schroeder, Wilfrid and Justice, Christopher O. , doi =. Remote Sensing of Environment , keywords =
-
[62]
doi:10.1007/978-3-030-87045-4_4 , file =
Liu, Yongqiang and Heilman, Warren E and Potter, Brian E and Clements, Craig B and Jackson, William A and French, Nancy H F and Goodrick, Scott L and Kochanski, Adam K and Larkin, Narasimhan K and Lahm, Peter W and Brown, Timothy J and Schwarz, Joshua P and Strachan, Sara M and Zhao, Fengjun and Liu, Yongqiang and Goodrick, Scott L and Zhao,. doi:10.1007/...
-
[63]
Remote Sensing , keywords =
Liu, Xiangzhuo and He, Binbin and Quan, Xingwen and Yebra, Marta and Qiu, Shi and Yin, Changming and Liao, Zhanmang and Zhang, Hongguo , doi =. Remote Sensing , keywords =
-
[64]
and Wulder, Michael A
Ban, Yifang and Zhang, Puzhao and Nascetti, Andrea and Bevington, Alexandre R. and Wulder, Michael A. , doi =. Scientific Reports , keywords =
-
[65]
and Johnson, E.A
Bakhshaii, A. and Johnson, E.A. A. , doi =. Canadian Journal of Forest Research , keywords =
-
[66]
and Randerson, James T
Chen, Yang and Morton, Douglas C. and Randerson, James T. , doi =. One Earth , month =
-
[67]
Haines, Donald A. and Smith, Mahlon C. , booktitle =. doi:10.1175/1520-0450(1987)026 , file =
-
[68]
Johnston, Joshua M. and Jackson, Natasha and Mcfayden, Colin and Phong, Linh Ngo and Lawrence, Brian and Davignon, Didier and Wooster, Martin J. and. Sensors 2020, Vol. 20, Page 5081 , keywords =. doi:10.3390/s20185081 , file =
-
[69]
Journal of Environmental Management , keywords =
Yoo, Seungmin and Kang, Won Hee and Song, Junho , doi =. Journal of Environmental Management , keywords =
-
[70]
Geoscientific Model Development , month =
Turquety, Sol. Geoscientific Model Development , month =. doi:10.5194/GMD-13-2981-2020 , file =
-
[71]
and Chen, Yang and Morton, Douglas C
Liu, Tianjia and Randerson, James T. and Chen, Yang and Morton, Douglas C. and Wiggins, Elizabeth B. and Smyth, Padhraic and Foufoula-Georgiou, Efi and Nadler, Roy and Nevo, Omer , doi =. Earth System Science Data , month =
-
[72]
and Humber, Michael L
Giglio, Louis and Boschetti, Luigi and Roy, David P. and Humber, Michael L. and Justice, Christopher O. , doi =. Remote Sensing of Environment , keywords =
-
[73]
and Ilavajhala, Shriram and Wong, Min Minnie and Justice, Christopher O
Davies, Diane K. and Ilavajhala, Shriram and Wong, Min Minnie and Justice, Christopher O. , doi =. IEEE Transactions on Geoscience and Remote Sensing , keywords =
-
[74]
and Johnston, Joshua M
Allison, Robert S. and Johnston, Joshua M. and Craig, Gregory and Jennings, Sion , doi =. Sensors 2016, Vol. 16, Page 1310 , keywords =
2016
-
[75]
, file =
Rothermel, Richard C.; Deeming, John E. , file =
-
[76]
Science of The Total Environment , keywords =
Yang, Songxi and Huang, Qunying and Yu, Manzhu , doi =. Science of The Total Environment , keywords =
-
[77]
and Monedero, Santiago and Quinones, Tomas and Little, Kerryn and Stoof, Cathelijne R
Cardil, Adrian and Tapia, Victor M. and Monedero, Santiago and Quinones, Tomas and Little, Kerryn and Stoof, Cathelijne R. and Ramirez, Joaquin and De-Miguel, Sergio , doi =. Natural Hazards and Earth System Sciences , month =
-
[78]
International Geoscience and Remote Sensing Symposium (IGARSS) , keywords =
Liu, Xiangzhuo and He, Binbin and Quan, Xingwen and Wen, Chongbo and Liu, Xiaofang , doi =. International Geoscience and Remote Sensing Symposium (IGARSS) , keywords =
-
[79]
and Hassan, Quazi K
Chowdhury, Ehsan H. and Hassan, Quazi K. , doi =. ISPRS Journal of Photogrammetry and Remote Sensing , keywords =
-
[80]
Current Opinion in Environmental Science & Health , keywords =
Cardil, Adri. Current Opinion in Environmental Science & Health , keywords =. doi:10.1016/J.COESH.2021.100291 , issn =
-
[81]
Journal of Forestry Research 2005 16:1 , keywords =
Xlao-Rul, Tian and Mcrae, Douglas J and Li-Fu, Shu and Wang, Ming-Yu and Li, Hong , doi =. Journal of Forestry Research 2005 16:1 , keywords =
2005
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