Google Scholar Link

1. Wang, F., Xiang, L., Sze-Yin Leung, K., Elsner, M., Zhang, Y., Guo, Y., Pan, B., Sun, H., An, T., Ying, G., Brooks, B.W, Hou, D., Helbling, D.E., Sun, J., Qiu, H., Vogel, T.M., Zhang, W., Gao, Y., Simpson, M.J., Luo, Y., Chang, S.X., Su, G., Wong, B.M., Fu, T.-M., Zhu, D., Jobst, K.J., Ge, C., Coulon, F., Harindintwali, J.D., Zeng, X., Wang, H., Fu, Y., Wei, Z., Lohmann, R., Chen, C., Song, Y., Sanchez-Cid, C., Wang, Y., El-Naggar, A., Yao, Y., Huang, Y., Cheuk-Fung Law, J., Gu, C.,Shen, H., Gao, Y., Qin, C., Li, H., Zhang, T., Corcoll, N., Liu, M., Alessi, D.S., Li, H., Brandt, K.K., Pico, Y., Gu, C., Guo, J., Su, J., Corvini, P., Ye, M., Rocha-Santos, T., He, H., Yang, Y., Tong, M., Zhang, W., Suanon, F., Brahushi, F., Wang, Z., Hashsham, S.A., Virta, M., Yuan, Q., Jiang, G., Tremblay, L.A., Bu, Q., Wu, J., Peijnenburg, W., Topp, E., Cao, X., Jiang, X., Zheng, M., Zhang, T., Luo, Y., Zhu, L., Li, X., Barceló, D., Chen, J., Xing, B., Amelung, W., Cai, Z., Naidu, R., Shen, Q., Pawliszyn, J., Zhu, Y.-g., Schaeffer, A., Rillig, M.C., Wu, F., Yu, G., and J.M. Tiedje. (2024) “Emerging Contaminants: A One Health Perspective,” The Innovation, DOI: 10.1016/j.xinn.2024.100612.
2. Martin, M, Wu, J., Rich, S.L., Richardson, R.E., and D.E. Helbling. (2024) “Differential biotransformation of micropollutants in conventional activated sludge and up-flow anaerobic sludge blanket processes,” Environmental Science: Water Research & Technology, 10, 936 – 948.
3. Lin, Z.-W., Shapiro, E.F., Barajas-Rodriguez, F.J., Gaisin, A., Ateia, M., Currie, J., Helbling, D.E., Gwinn, R., Packman, A.I., and W.R. Dichtel. (2023) “Trace organic contaminant removal from municipal wastewater by styrenic β-cyclodextrin polymers,” Environmental Science & Technology, 57, 48, 19624–19636.
4. Joseph, N., Schwichtenberg, T., Jones, G., Rodowa, A., Barlaz, M., Cao, D., Charbonnet, J., Higgins, C.P., Field, J. and D.E. Helbling. (2023) “Target and suspect screening integrated with machine learning to discover PFAS source fingerprints,” Environmental Science & Technology, 57, 38, 14351–14362.
5. Georgakakos, C.B., Martínez, C.E., Helbling, D.E., and M.T. Walter. (2023) “More movement with manure: increased mobility of erythromycin through agricultural soil in the presence of manure,” Journal of Water and Health, 21 (9): 1143–1157.
6. Pan, Y. and D.E. Helbling. (2023) “Revealing the factors resulting in incomplete recovery of perfluoroalkyl acids (PFAAs) when implementing the adsorbable and extractable organic fluorine methods,” Water Research, 244, 120497.
7. Jacob, P. and D.E. Helbling. (2023) “Exploring the evolution of organofluorine-containing compounds during simulated photolithography experiments,” Environmental Science & Technology, 57, 34, 12819–12828.
8. Rich, S.L. and D.E. Helbling. (2023) “Daily micropollutant monitoring at a full-scale wastewater treatment plant reveals temporal trends in biotransformation rate constants influenced by chemical structure,” Environmental Science & Technology, 57, 28, 10404–10414.
9. Hu, J., Li, S., Zhang, W., Helbling, D.E., Xu, N., Sun, W., and J. Ni. (2023) “Animal production predominantly contributes to antibiotic profiles in the Yangtze River,” Water Research, 242, 120214.
10. Stults, J., Higgins, C.P., and D.E. Helbling. (2023) “Integration of per- and polyfluoroalkyl substance (PFAS) fingerprints in fish with machine learning for PFAS source tracking in surface water,” Environmental Science & Technology Letters, 10, 11, 1052–1058.
11. Ching, C., Lin, Z.W., Dichtel, W.R., and D.E. Helbling. (2023) “Evaluating the performance of novel cyclodextrin polymer granules to remove perfluoroalkyl acids (PFAAs) from water,” ACS ES&T Engineering, 3, 5, 661–670.
12. Tarpeh, W.A., Du, Y., Carpenter, C.M.G., Rodriguez, E., Helbling, D.E., Aga, D., Love, N.G., and K.R. Wigginton. (2023) “A unit process approach to nontarget screening of organic contaminants during urine treatment,” ACS ES&T Engineering, 3, 4, 590–601.
13. Jacob, P. and D.E. Helbling. (2023) “Rapid and simultaneous quantification of short- and ultrashort-chain perfluoroalkyl substances in water and wastewater,” ACS ES&T Water, 3, 1, 118–128.
14. Charbonnet, J.A., McDonough, C.A., Xiao, F., Schwichtenberg, T., Cao, D., Kaserzon, S., Thomas, K.V., Dewapriya, P., Place, B.J., Schymanski, E.L., Field, J.A., Helbling, D.E., and C.P. Higgins. (2022) “Communicating confidence of per- and polyfluoroalkyl substance (PFAS) identification via high-resolution mass spectrometry,” Environmental Science & Technology Letters, 9, 6, 473–481. Recipient of ES&T Letters Best Paper Award.
15. Wang, R., Lin, Z.W., Klemes, M.J., Ateia, M., Trang, B., Wang, J., Ching, C., Helbling, D.E., and W.R. Dichtel. (2022) “A tunable porous β-cyclodextrin polymer platform to understand and improve anionic PFAS removal,” ACS Central Science, 8, 5, 663–669.
16. Hübner, U., Wurtzbacher, C., Helbling, D.E., and J.E. Drewes. (2022) “Engineering of managed aquifer recharge systems to optimize biotransformation of trace organic chemicals,” Current Opinion in Environmental Science & Health, 27, 100343.
17. Sherman, A., Mejia, W.A.G., Padilla, N.R., Carpenter, C.M.G., Rich, S.L., Moncada, E.A.T., and D.E. Helbling. (2022) “Target and suspect screening for pesticides in the drinking water resources of Honduras,” H2Open Journal, 5, 1, 83-96.
18. Choi, Y.J., Helbling, D.E., Liu, J., Oliveras Martinez, C.I., and C.P. Higgins. (2022) “Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances,” Science of the Total Environment, 824, 153711.
19. Rich, S.L., Zumstein, M.T., and D.E. Helbling. (2022) “Identifying functional groups that determine the rates of micropollutant biotransformations performed by wastewater microbial communities,” Environmental Science & Technology, 56, 984-994.
20. Ching, C., Ling, Y., Trang, B., Klemes, M., Xiao, L., Yang, A., Barin, G., Dichtel, W.R., and D.E. Helbling. (2022) “Identifying the physicochemical properties of β-cyclodextrin polymers that determine the adsorption of perfluoroalkyl acids,” Water Research, 209, 117938.
21. Jacob, P., Wang, R., Ching, C., and D.E. Helbling. (2021) “Evaluation, optimization, and application of three independent suspect screening workflows for the characterization of PFASs in water,” Environmental Science: Processes & Impacts, 23, 1554 – 1565. Selected for RSC curated collection PFAS: cleaning up drinking water (2023).
22. Charbonnet, J.A., Rodowa, A.E., Joseph, N.T., Guelfo, J.I., Jones, G.D., Field, J.A., Higgins, C.P., Helbling, D.E., and E. F. Houtz. (2021) “Environmental source tracking of per- and polyfluoroalkyl substances within a forensic context: current and future techniques,” Environmental Science & Technology, 55, 11, 7237–7245.
23. Jacob, P., Barzen-Hanson, K., and D.E. Helbling. (2021) “Target and nontarget analysis of per- and polyfluoralkyl substances in wastewater from electronics fabrication facilities,” Environmental Science & Technology, 55, 4, 2346–2356.
24. Wang, R., Ching, C., Dichtel, W.R., and D.E. Helbling. (2020) “Evaluating the removal of per- and polyfluoroalkyl substances from contaminated groundwater with different adsorbents using a suspect screening approach,” Environmental Science & Technology Letters, 7, 12, 954–960.
25. Ateia, M., Helbling, D.E., and W.R. Dichtel. (2020) “Best practices for evaluating new materials as adsorbents for water treatment,” ACS Materials Letters, 2, 11, 1532–1544.
26. Ching, C., Klemes, M.J., Trang, B., Dichtel, W.R., and D.E. Helbling. (2020) “β-cyclodextrin polymers with different crosslinkers and ion exchange resins exhibit variable adsorption of anionic, zwitterionic, and nonionic PFASs,” Environmental Science & Technology, 54, 19, 12693–12702.
27. Klemes, M.J., Skala, L., Ateia, M., Trang, B., Helbling, D.E., and W.R. Dichtel. (2020) “Polymerized molecular receptors as adsorbents to remove micropollutants from water,” Accounts of Chemical Research, 53, 10, 2314–2324.
28. Yang, A., Ching, C., Easler, M., Helbling, D.E. and W.R. Dichtel. (2020) “Cyclodextrin polymers with nitrogen-containing tripodal crosslinkers for efficient PFAS adsorption,” ACS Materials Letters, 2, 1240−1245.
29. Zumstein, M.T., Werner, J.J., and D.E. Helbling. (2020) “Exploring the specificity of extracellular wastewater peptidases to inform the design of sustainable peptide-based antibiotics,” Environmental Science & Technology, 54, 18, 11201–11209.
30. Lin, Y., Sevillano Rivera, M., Jiang, T., Li, G., Cotto, I., Vosloo, S., Carpenter, C.M.G., Larese-Casanova, P., Giese, R., Helbling, D.E., Padilla, I., Rosario-Pabón, Z., Cordero, J., Vélez Vega, C., Alshawabkeh, A., Pinto, A., and A.Z. Gu. (2020) “Impact of Hurricane Maria on drinking water quality in Puerto Rico,” Environmental Science & Technology, 54, 9495–9509.
31. Wu, C., Klemes, M.J., Trang, B., Dichtel, W.R., and D.E. Helbling. (2020) “Exploring the factors that influence the adsorption of anionic PFAS on conventional and emerging adsorbents in aquatic matrices,” Water Research, 182, 115950.
32. Ling, Y., Alzate-Sánchez, D.M., Klemes, M.J., Dichtel, W.R., and D.E. Helbling. (2020) “Evaluating the effects of water matrix constituents on micropollutant removal by activated carbon and β-cyclodextrin polymer adsorbents,” Water Research, 173, 115551.
33. Wang, Y., Fenner, K., and D.E. Helbling. (2020) “Clustering micropollutants based on initial biotransformations for improved prediction of micropollutant removal during conventional activated sludge treatment,” Environmental Science: Water Research & Technology, 6, 554 – 565.
34. Carpenter, C.M.G., Wong, L.Y.J., Gutema, D., and D.E. Helbling.* (2019) “Fall Creek Monitoring Station: using environmental covariates to predict micropollutant dynamics and peak events in surface water systems,” Environmental Science & Technology, 53, 8599−8610.
35. Klemes, M.J., Ling, Y., Ching, C., Wu, C., Xiao, L., Helbling, D.E., and W.R. Dichtel. (2019) “Reduction of a tetrafluoroterephthalonitrile-β-cyclodextrin polymer to remove anionic micropollutants and perfluorinated alkyl substances from water,” Angewandte Chemie, 58, 12049-12053.
36. Bamberger, M., Nell, M., Ahmed, A.H., Santoro, R., Ingraffea, A.R., Kennedy, R.F., Nagel, S.C., Helbling, D.E., and R.E. Oswald. (2019) “Surface water and groundwater analysis using aryl hydrocarbon and endocrine receptor biological assays and liquid chromatography-high resolution mass spectrometry in Susquehanna County, PA,” Environmental Science: Processes & Impacts, 21, 988–998.
37. Xiao, L., Ching, C., Ling, Y., Nasiri, M., Klemes, M.J., Reineke, T.M., Helbling, D.E., and W.R. Dichtel. (2019) “Crosslinker chemistry determines the uptake potential of perfluorinated alkyl substances by β-cyclodextrin polymers,” Macromolecules, 52, 10, 3747-3752.
38. Gao, H., LaVergne, J.M., Carpenter, C.M.G., Desai, R., Zhang, X., Gray, K., Helbling, D.E., and G.F. Wells (2019) “Exploring co-occurrence patterns between organic micropollutants and bacterial community structure in a mixed-use watershed,” Environmental Science: Processes & Impacts, 21, 861-880.
39. Liu, L., Helbling, D.E., Kohler, H.-P.E., and B. Smets. (2019) “Modelling carbofuran biotransformation by Novosphingobium sp. KN65.2 in the presence of coincidental carbon and indigenous microbes,” Environmental Science: Water Research & Technology, 5, 798–807.
40. Zumstein, M.T. and D.E. Helbling. (2019) “Biotransformation of antibiotics: exploring the activity of extracellular and intracellular enzymes derived from wastewater microbial communities,” Water Research, 155, 115-123.
41. Alzate-Sanchez, D.M., Ling, Y., Li, C., Frank, B.P., Bleher, R., Fairbrother, H., Helbling, D.E., and W.R. Dichtel. (2019) “β-Cyclodextrin polymers on microcrystalline cellulose as a granular media for organic micropollutant removal from water,” ACS Applied Materials & Interfaces, 11, 8, 8089-8096.
42. Ling, Y., Klemes, M., Steinschneider, S., Dichtel, W.R., and D.E. Helbling. (2019) “QSARs to predict adsorption affinity of organic micropollutants for activated carbon and β-cyclodextrin polymer adsorbents,” Water Research, 154, 217-226.
43. Carpenter, C.M.G., Wong, L.Y.J., Johnson, C., and D.E. Helbling. (2019) “Fall Creek Monitoring Station: Highly resolved temporal sampling to prioritize the identification of non-target micropollutants,” Environmental Science & Technology, 53(1), 77−87. Selected for ACS Editors’ Choice (December 12, 2018).
44. Nell, M. and D.E. Helbling (2019) “Exploring matrix effects and quantifying organic additives in hydraulic fracturing associated fluids using liquid chromatography electrospray ionization mass spectrometry,” Environmental Science: Processes & Impacts, 21, 195–205.
45. Ji, W., Xiao, L., Ling, Y., Ching, C., Matsumoto, M., Bisbey, R.P., Helbling, D.E., and W.R. Dichtel. (2018) “Removal of GenX  and perfluorinated alkyl substances from water by amine-functionalized covalent organic frameworks,” Journal of the American Chemical Society, 140(40), 12677−12681. Tagged as “Highly Cited Paper” in the field of Environment/Ecology (Web of Science).
46. Klemes, M.J., Ling, Y., Chiapasco, M., Alsbaiee, A., Helbling, D.E., and W.R. Dichtel. (2018) “Phenolation of cyclodextrin polymers controls their lead and organic micropollutant adsorption,” Chemical Science, 9, 8883–8889.
47. Wang, Y., Lai, A., Latino, D., Fenner, K., and D.E. Helbling. (2018) “Evaluating the environmental parameters that determine aerobic biodegradation half-lives of pesticides in soil with a multivariable approach,” Chemosphere, 209 (2018) 430-438.
48. Carpenter, C.M.G. and D.E. Helbling (2018) “Widespread micropollutant monitoring in the Hudson River Estuary reveals spatiotemporal micropollutant clusters and their sources,” Environmental Science & Technology, 52(11), 6187–6196.
49. Li, C., Klemes, M.J., Dichtel, W.R., and D.E. Helbling. (2018) “Tetrafluoroterephthalonitrile-crosslinked β-cyclodextrin polymers for efficient extraction and recovery of organic micropollutants from water,” Journal of Chromatography A, 1541(2018) 52–56.
50. Oetjen, K., Danforth, C., McLaughlin, M., Nell, M., Blotevogel, J., Helbling, D.E., Mueller, D., and C.P. Higgins. (2017) “Emerging analytical methods for the characterization and quantification of organic contaminants in flowback and produced water,” Trends in Environmental Analytical Chemistry, 15(2017), 12-23.
51. Ling, Y., Klemes, M.J., Xiao, L., Alsbaiee, A., Dichtel, W.R., and D.E. Helbling. (2017) “Benchmarking micropollutant removal by activated carbon and porous β-cyclodextrin polymers under environmentally relevant scenarios,” Environmental Science & Technology, 51(13), 7590–7598.
52. Xiao, L., Ling, Y., Alsbaiee, A., Li, C., Helbling, D.E., and W.R. Dichtel. (2017) “A β-cyclodextrin polymer network sequesters PFOA at environmentally relevant concentrations,” Journal of the American Chemical Society, 139(23), 7689–7692. Selected for ACS Editors’ Choice (June 6, 2017); Tagged as “Highly Cited Paper” in the field of Environment/Ecology (Web of Science).
53. Carpenter, C.M.G. and D.E. Helbling. (2017) “Removal of micropollutants in biofilters: hydrodynamic effects on biofilm assembly and functioning,” Water Research, 120, 211-221.
54. Pochodylo, A.L., and D.E. Helbling. (2017) “Emerging Investigators Series: Prioritization of suspect hits in a sensitive suspect screening workflow for comprehensive micropollutant characterization in environmental samples,” Environmental Science: Water Research & Technology, 3, 54-65. Featured on the Cover of the Journal; Featured as part of Emerging Investigators Series.
55. Men, Y., Achermann, S., Helbling, D.E., Johnson, D.R., and K. Fenner. (2017) “Relative contribution of ammonia oxidizing bacteria and other members of nitrifying activated sludge communities to micropollutant biotransformation,” Water Research, 109, 217-226.
56. Wang, M. and D.E. Helbling (2016) “A non-target approach to identify disinfection byproducts of structurally similar sulfonamide antibiotics,” Water Research, 102, 241-251.
57. Men, Y., Han, P., Helbling, D.E., Jehmlich, N., Herbold, C., Gulde, R., Onnis-Hayden, A., Gu, A.Z., Johnson, D.R., Wagner, M., and K. Fenner (2016) “Biotransformation of two pharmaceuticals by the ammonia-oxidizing archaeon Nitrososphaera gargensis,” Environmental Science & Technology, 50(9), 4682-4692.
58. Gulde, R., Meier, U., Schymanski, E.L., Kohler, H.-P.E., Helbling, D.E., Derrer, S., Rentsch, D., and K. Fenner. (2016) “Systematic exploration of biotransformation reactions of amine-containing micropollutants in activated sludge,” Environmental Science & Technology, 50(6), 2908-2920.
59. Alsbaiee, A., Smith, B.J., Xiao, L., Ling, Y., Helbling, D.E., and W.R. Dichtel. (2016) “Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer,” Nature, 529, 190-194. Featured on the Cover of the Journal; Tagged as “Highly Cited Paper” in the field of Environment/Ecology (Web of Science). 
60. Johnson, D.R., Helbling, D.E., Men, Y., and K. Fenner. (2015) “Can meta-omics help to establish causality between contaminant biotransformations and genes or gene products?,” Environmental Science: Water Research & Technology, 1, 272–278.
61. D.E. Helbling. (2015) “Bioremediation of pesticide-contaminated water resources: the challenge of low concentrations,” Current Opinion in Biotechnology, 33 142-148.
62. Helbling, D.E., Johnson, D.R., Lee, T.K., Scheidegger, A., and K. Fenner. (2015) “A framework for establishing predictive relationships between specific bacterial 16S rRNA sequence abundances and biotransformation rates,” Water Research, 70 471-484.
63. Johnson, D.R., Helbling, D.E., Lee, T.K., Park, J., Fenner, K., Kohler, H.-P.E. and M. Ackermann. (2015) “Association of biodiversity with the rates of micropollutant biotransformations among full-scale wastewater treatment plant communities,” Applied and Environmental Microbiology, 81(2) 666-675.
64. Johnson, D.R., Lee, T.K., Park, J., Fenner, K., and D.E. Helbling. (2015) “The functional and taxonomic richness of wastewater treatment plant microbial communities are associated with each other and with ambient nitrogen and carbon availability,” Environmental Microbiology, 17(12) 4851-4860.
65. Gulde, R., Helbling, D.E., Scheidegger, A., and K. Fenner. (2014) “pH-dependent biotransformation of ionizable organic micropollutants in activated sludge,” Environmental Science & Technology, 48(23) 13760-13768. Second Runner-Up, ES&T Editor’s Choice Award – Best Environmental Science Paper of 2014
66. Liu, L., Helbling, D.E., Kohler, H.-P.E., and B. Smets.  (2014) “A model framework to describe growth-linked biodegradation of trace-level pollutants in the presence of coincidental carbon substrates and microbes,” Environmental Science & Technology, 48(22) 13358-13366.
67. Nguyen, T.P.O., Helbling, D.E., Bers, K., Fida, T., Wattiez, R., Kohler, H.-P.E., De Mot, R., and D. Springael. (2014) “Genetic and metabolic analysis of the carbofuran catabolic pathway in Novosphingobium sp. KN65.2,” Applied Microbiology and Biotechnology, 98(19) 8235-8253.
68. Madureira, D.J., Weiss, F.T., Van Midwoud, P., Helbling, D.E., Sturla, S., and K. Schirmer. (2014) “A systems toxicology approach to understand the kinetics of benzo(a)pyrene uptake, biotransformation and DNA adduct formation in a liver cell model,” Chemical Research in Toxicology, 27(3) 443-453.
69. Kolvenbach, B.A., Helbling, D.E., Kohler, H.-P.E., and P.F.-X. Corvini. (2014) “Emerging chemicals and the evolution of biodegradation capacities and pathways in bacteria,” Current Opinion in Biotechnology, 27 8-14.
70. Helbling, D.E., Hammes, F., Egli, T., and H.-P.E. Kohler. (2014) “Kinetics and yields of pesticide biodegradation at low substrate concentrations and under conditions restricting assimilable organic carbon,” Applied and Environmental Microbiology, 80(4) 1306-1313.
71. Benner, J., Helbling, D.E., Kohler, H.-P.E., Wittebol, J., Kaiser, E., Prasse, C., Ternes, T.A., Albers, C.N., Aamand, J., Horemans, B., Springael, D., Walravens, E., and N. Boon. (2013) “Is biological treatment a viable alternative for micropollutant removal in drinking water treatment processes?,” Water Research, 47(16) 5955-5976.
72. Helbling, D.E., Johnson, D.R., Honti, M., and K. Fenner. (2012) “Micropollutant biotransformation kinetics  associate with WWTP process parameters and microbial community characteristics,” Environmental Science & Technology, 46(19) 10579-10588.
73. Helbling, D.E., Ackermann, M., Fenner, K., Kohler, H-P.E., and D.R. Johnson. (2011) “The activity level of a microbial community function can be predicted from its metatranscriptome,”  International Society of Microbial Ecology Journal, 6(4) 902-904.
74. Kern, S., Baumgartner, R., Helbling, D.E., Hollender, J., Singer, H., Loos, M., Schwarzenbach, R., and K. Fenner. (2010) “A tiered procedure for assessing the formation of biotransformation products of pharmaceuticals and biocides during activated sludge treatment,”  Journal of Environmental Monitoring, 12(11) 2100-2111.
75. Helbling, D.E., Hollender, J., Kohler, H-P.E., and K. Fenner. (2010) “A structure-based interpretation of biotransformation pathways of amide-containing compounds in sludge-seeded bioreactors,”  Environmental Science & Technology, 44(17) 6628-6635.
76. Helbling, D.E., Hollender, J., Kohler, H-P.E., Singer, H., and K. Fenner. (2010) “High-throughput identification of microbial transformation products of organic micropollutants,” Environmental Science & Technology, 44(17) 6621-6627.  ES&T Editor’s Choice Award – Best Environmental Science Paper of 2010
77. Helbling, D.E. and J.M. VanBriesen. (2009) “Modeling residual chlorine response to a microbial contamination event in drinking water distribution systems,” Journal of Environmental Engineering, 135(10) 918-927.
78. Helbling, D.E. and J.M. VanBriesen. (2008) “Continuous monitoring of residual chlorine concentrations in response to controlled microbial intrusions in a laboratory-scale distribution system,” Water Research, 42(12) 3162-3172.
79. Helbling, D.E. and J.M. VanBriesen. (2007) “Free chlorine demand and cell survival of microbial suspensions,” Water Research, 41(19) 4424-4434.