Bridging Learning Styles: How the GASING Method Fosters Inclusive Conceptual Understanding of Integers
-
Purpose of the study: Despite growing evidence of the GASING (Easy, Fun, and Enjoyable) method’s effectiveness, little is known about whether its benefits hold consistently across students with different learning styles. This study addressed that gap by analyzing improvements in junior high school students’ conceptual understanding of integers through the GASING method, examined in relation to students’ learning styles (visual, auditory, kinesthetic).
Methodology: A quantitative quasi-experimental nonequivalent control group design (2×3 factorial) was employed with 54 Grade VII students (27 per group) from a public junior high school in Humbang Hasundutan Regency. Data were collected using a conceptual understanding test (pretest-posttest) and a learning style questionnaire and analyzed with the Mann-Whitney U test, Kruskal-Wallis test, and two-way ANOVA (α = 0.05).
Main Findings: Both groups had equivalent prior ability (p = 0.944). The experimental class achieved a significantly higher mean posttest score (90.60 vs. 80.06) and N-Gain (0.885 vs. 0.739; p < 0.001, large effect size d = 1.19). We found no significant differences by learning style or its interaction with teaching method (p > 0.05).
Novelty/Originality of this study: This study provides novel evidence that the GASING method is equally effective for visual, auditory, and kinesthetic learners, demonstrating its inclusive multisensory design and eliminating the need for differentiated instruction based on learning style in integer learning at the junior high school level. Practically, this means teachers can use a single, unified GASING lesson design in heterogeneous classrooms, reducing planning burden while still meeting diverse learners’ needs.
-
How to cite
[1]“Bridging Learning Styles: How the GASING Method Fosters Inclusive Conceptual Understanding of Integers”, Jor. Eva. Edu, vol. 7, no. 4, pp. 772–784, Oct. 2026, doi: 10.37251/jee.v7i4.3504. -
17Abstract views5Downloads
Metrics — Badges
-
- [1] R. Kurniasi, N. Nurjanah, and E. Cahya, “Students’ learning obstacle in operations of integer,” Educenter: Jurnal Ilmiah Pendidikan, vol. 3, no. 1, pp. 59–66, 2024, doi: 10.55904/educenter.v3i1.1107.
- [2] A. Canogullari and M. Isiksal-Bostan, “Middle school mathematics teachers’ knowledge of integers,” European Journal of Science and Mathematics Education, vol. 12, no. 2, pp. 312–325, 2024, doi: 10.30935/scimath/14439.
- [3] Kemdikbud, Kurikulum Merdeka: Panduan Pembelajaran Matematika untuk SMP. Jakarta, Indonesia: Kementerian Pendidikan, Kebudayaan, Riset, dan Teknologi Republik Indonesia, 2021.
- [4] B. M. Suryonegoro, Wardono, S. B. Waluya, M. Mulyono, and I. B. Wijaya, “A systematic review of junior high school mathematics curriculum in Indonesia and Australia,” Journal Evaluation in Education (JEE), vol. 7, no. 1, pp. 291–305, 2026, doi: 10.37251/jee.v7i1.2472.
- [5] R. M. Jauzaa, N. Nurmitasari, and R. Cahyadi, “Implementasi kurikulum merdeka belajar pada pembelajaran matematika [Implementation of the 'Merdeka Belajar' (Freedom to Learn) curriculum in mathematics instruction],” Eksponen, vol. 14, no. 1, pp. 40–47, 2024, doi: 10.47637/eksponen.v14i1.1017.
- [6] National Council of Teachers of Mathematics (NCTM), Principles and Standards for School Mathematics. Reston, VA, USA: NCTM, 2000.
- [7] N. Suprapto, “Do we experience misconceptions?: An ontological review of misconceptions in science,” Stud. Philos. Sci. Educ., vol. 1, no. 2, pp. 50–55, 2020, doi: 10.46627/sipose.v1i2.28.
- [8] S. Fuadiah, D. Suryadi, and T. Turmudi, “Concept misunderstanding of negative numbers among students,” J. Math. Educ., vol. 7, no. 2, pp. 123–130, 2016, doi: 10.22342/jme.7.2.3537.123-130.
- [9] G. Putri, M. Maison, and N. Huda, “Studi struktur kognitif miskonsepsi siswa pada materi operasi hitung bilangan bulat [Study of the cognitive structure of students' misconceptions on the material of integer arithmetic operations],” Jurnal Cendekia: Jurnal Pendidikan Matematika, vol. 5, no. 3, pp. 3097–3107, 2021, doi: 10.31004/cendekia.v5i3.1064.
- [10] C. Ainia and M. F. Amir, “Analysis of elementary school students’ difficulties in solving integer word problems,” MaPan: Jurnal Matematika dan Pembelajaran, vol. 9, no. 2, pp. 304–318, 2021, doi: 10.24252/mapan.2021v9n2a9.
- [11] Y. Yanala, M. Isa, and C. A. Uke, “Analisis pemahaman konsep matematika pada materi operasi bilangan bulat di SMP Negeri 4 Gorontalo [An analysis of the understanding of mathematical concepts regarding integer operations at SMP Negeri 4 Gorontalo],” Jambura Journal of Mathematics Education, vol. 2, no. 2, pp. 61–68, 2021, doi: 10.34312/jmathedu.v2i2.10618.
- [12] D. W. Maulida and Sutama, “Mathematics misconceptions in completing the calculation operation of subtraction of integers in junior high school,” AIP Conference Proceedings, vol. 3412, no. 1, pp. 020124, 2026, doi: 10.1063/5.0318398.
- [13] T. N. Sipayung and D. Anzelina, “An analysis of students problem solving skills using a realistic mathematics approach on integers materials,” J. Phys. Conf. Ser., vol. 1211, no. 1, p. 012083, 2019, doi: 10.1088/1742-6596/1211/1/012083.
- [14] J. C. Sercenia, E. Ibañez, and J. Pentang, “Thinking beyond thinking: Junior high school students’ metacognitive awareness and conceptual understanding of integers,” Mathematics Teaching-Research Journal, vol. 15, no. 1, pp. 4–24, 2023.
- [15] OECD, PISA 2022 Results (Volume I): The State of Learning and Equity in Education. Paris, France: OECD Publishing, 2023, doi: 10.1787/53f23881-en.
- [16] J. Kilpatrick, J. Swafford, and B. Findell, Eds., Adding It Up: Helping Children Learn Mathematics. Washington, DC, USA: National Academy Press, 2001.
- [17] M. N. Kholid, A. Imawati, A. Swastika, S. Maharani, and L. N. Pradana, “How are students’ conceptual understanding for solving mathematical problem?,” J. Phys. Conf. Ser., vol. 1776, no. 1, p. 012018, 2021, doi: 10.1088/1742-6596/1776/1/012018.
- [18] R. Skemp, “Relational understanding and instrumental understanding,” Math. Teach., vol. 77, pp. 20–26, 1976.
- [19] A. Sfard, “On the dual nature of mathematical conceptions: Reflections on processes and objects as different sides of the same coin,” Educ. Stud. Math., vol. 22, no. 1, pp. 1–36, 1991, doi: 10.1007/BF00302715.
- [20] T. P. Carpenter and R. Lehrer, “Teaching and learning mathematics with understanding,” in Mathematics Classrooms That Promote Understanding, E. Fennema and T. R. Romberg, Eds. Mahwah, NJ, USA: Lawrence Erlbaum Associates, 1999, pp. 19–32.
- [21] M. D. Merrill, “First principles of instruction,” Educ. Technol. Res. Dev., vol. 50, no. 3, pp. 43–59, 2002, doi: 10.1007/BF02505024.
- [22] S. Sulistiawati, “Pembelajaran matematika GASING ditinjau dari berbagai perspektif teori belajar [GASING mathematics learning is reviewed from various learning theory perspectives],” Teorema: Teori dan Riset Matematika, vol. 4, no. 1, pp. 41–54, 2019, doi: 10.25157/teorema.v4i1.1701.
- [23] J. S. Bruner, Toward a Theory of Instruction. Cambridge, MA, USA: Harvard University Press, 1966.
- [24] D. Kolb, Experiential Learning: Experience as the Source of Learning and Development. Englewood Cliffs, NJ, USA: Prentice Hall, 1984.
- [25] J. A. Van de Walle, K. S. Karp, and J. M. Bay-Williams, Elementary and Middle School Mathematics: Teaching Developmentally, 9th ed. Upper Saddle River, NJ, USA: Pearson, 2019.
- [26] I. Windani, S. Samron, A. L. Arua, and S. Safarudin, “Meningkatkan penguasaan konsep bilangan bulat dengan menggunakan metode GASING pada siswa kelas III SD Negeri 1 Batulo [Improving mastery of the concept of integers by using the GASING method in grade III students of SD Negeri 1 Batulo],” Jurnal Pendidikan Tambusai, vol. 7, no. 2, pp. 19181–19192, 2023, doi: 10.31004/jptam.v7i2.14295.
- [27] O. R. Lestari and A. T. A. Hardini, “Keefektifan metode matematika GASING dalam meningkatkan kemampuan pemahaman konsep matematis perkalian dua digit untuk siswa kelas VI SD [The effectiveness of the GASING mathematical method in improving the ability to understand the mathematical concept of two-digit multiplication for sixth grade elementary school students],” Jurnal Kewarganegaraan, vol. 6, no. 2, pp. 2498–2506, 2022, doi: 10.31316/jk.v6i2.3038.
- [28] D. T. Tarusu and P. C. A. Pokaton, “Penerapan metode GASING untuk meningkatkan hasil belajar perkalian pada siswa kelas III SD Negeri 8 Tondano [Application of the GASING method to improve multiplication learning outcomes in grade III students of SD Negeri 8 Tondano],” J-CEKI: Jurnal Cendekia Ilmiah, vol. 3, no. 6, pp. 7870–7878, 2024, doi: 10.56799/jceki.v3i6.5727.
- [29] Y. Buknoni, W. Wahyudin, and S. B. Iriawan, “Efektivitas metode GASING untuk meningkatkan pemahaman konsep bilangan bulat di sekolah [The effectiveness of the GASING method for improving the understanding of integer concepts in schools],” Scholaria: Jurnal Pendidikan dan Kebudayaan, vol. 16, no. 2, pp. 194–203, 2026, doi: 10.24246/j.js.2026.v16.i2.p194-203.
- [30] J. Damopolii, W. Rorimpandely, and K. Ester, “Penggunaan model GASING dalam meningkatkan hasil belajar matematika operasi hitung perkalian pada murid kelas III [The use of the GASING model to improve the learning outcomes of mathematics multiplication operations in grade III students],” Jurnal Ilmiah Wahana Pendidikan, vol. 10, no. 3, pp. 1042–1052, 2024, doi: 10.5281/zenodo.10851212.
- [31] A. Armianti, I. Yani, K. Widuri, and S. Sulistiawati, “Pengaruh matematika GASING (Gampang, Asyik, dan Menyenangkan) pada materi perkalian bilangan bulat terhadap hasil belajar peserta matrikulasi STKIP Surya [The influence of the GASING (Easy, Fun, and Enjoyable) mathematics method—applied to the topic of integer multiplication—on the learning outcomes of matriculation program participants at STKIP Surya],” Kreano, Jurnal Matematika Kreatif-Inovatif, vol. 7, no. 1, pp. 74–81, 2018, doi: 10.15294/kreano.v7i1.5012.
- [32] H. Halyadi, D. Agustianie, T. Handayani, and H. Windria, “Penggunaan kobesi dalam matematika gasing untuk meningkatkan pemahaman materi perkalian siswa SD [The use of kobesi in the Gasing mathematics method to improve elementary school students' understanding of multiplication],” Suska Journal of Mathematics Education, vol. 2, no. 2, p. 81, 2017, doi: 10.24014/sjme.v2i2.2149.
- [33] A. Armianti, D. N. Wildan, R. Robiansyah, O. Trissiana, and R. C. I. Prahmana, “Peningkatan kemampuan pemahaman matematis siswa menggunakan pembelajaran Matematika GASING (Gampang, ASyIk, dan menyenaNGkan) [Improving students’ mathematical comprehension skills through the GASING (Easy, Fun, and Enjoyable) approach to mathematics learning],” Jurnal Elemen, vol. 2, no. 1, pp. 27–38, 2016, doi: 10.29408/jel.v2i1.152.
- [34] N. P. Yuliani, N. W. A. Antari, P. S. Wulandari, K. D. Saspanya, I. W. E. A. Prayoga, I. M. B. P. Yasa, and B. R. Werang, “Effectiveness of applying the GASING method in multiplication of two-digit numbers in elementary schools,” Formosa Journal of Applied Sciences, vol. 3, no. 7, pp. 3003–3018, 2024, doi: 10.55927/fjas.v3i7.9896.
- [35] E. S. Kresnawati, N. R. Dewi, B. Suprihatin, and Y. Resti, “Pengaruh penerapan konsep matematika GASING dalam meningkatkan kemampuan penjumlahan bilangan bulat guru SDIT Auladi Plaju [The effect of applying the GASING mathematical concept in improving the integer addition ability of SDIT Auladi Plaju teachers],” Jurnal Pengabdian Pada Masyarakat, vol. 6, no. 4, pp. 1076–1080, 2021, doi: 10.30653/002.202164.882.
- [36] M. W. K. Kusuma, I. N. Jampel, and G. W. Bayu, “Pengaruh metode pembelajaran matematika GASING terhadap hasil belajar matematika [The effect of the GASING mathematics learning method on mathematics learning outcomes],” Jurnal Pedagogi dan Pembelajaran, vol. 1, no. 1, pp. 37–46, 2018, doi: 10.23887/jp2.v1i1.19330.
- [37] B. DePorter and M. Hernacki, Quantum Learning: Membiasakan Belajar Cepat dan Menyenangkan [Quantum Learning: Getting Used to Fast and Enjoyable Learning]. Jakarta, Indonesia: PT Gramedia Pustaka Utama, 2004.
- [38] N. F. Fleming and C. Mills, “Not another inventory, rather a catalyst for reflection,” To Improve the Academy, vol. 11, no. 1, pp. 137–155, 1992, doi: 10.1002/j.2334-4822.1992.tb00213.x.
- [39] F. A. Dunn, “The learning styles questionnaire: A guide to learning style models and use in educational practice,” J. Educ. Psychol., vol. 41, no. 1, pp. 1–12, 2019, doi: 10.1037/edu0000301.
- [40] S. U. H. Fatonah and I. R. D. Nur, “Gaya belajar siswa dalam pembelajaran matematika di tingkat SMP [Student learning styles in mathematics learning at junior high school level],” RADIAN: Journal of Research and Review in Mathematics Education, vol. 1, no. 2, pp. 81–87, 2022, doi: 10.35706/rjrrme.v1i2.6534.
- [41] D. Supit, M. Melianti, E. M. M. Lasut, and N. J. Tumbel, “Gaya belajar visual, auditori, kinestetik terhadap hasil belajar siswa,” Journal on Education, vol. 5, no. 3, pp. 6994–7003, 2023, doi: 10.31004/joe.v5i3.1487.
- [42] Y. Yuniarti, Y. Abidin, and N. K. Restu, “Evaluating mathematical representation competence among primary students: Insights from the post-pandemic learning recovery,” Journal Evaluation in Education (JEE), vol. 6, no. 3, pp. 662–672, 2025, doi: 10.37251/jee.v6i3.1740.
- [43] S. Sugiyono, Metode Penelitian Kuantitatif, Kualitatif, dan R&D [Quantitative, Qualitative, and R&D Research Methods]. Bandung, Indonesia: Alfabeta, 2017.
- [44] J. W. Creswell, Research Design: Qualitative, Quantitative, and Mixed Methods Approaches, 4th ed. Thousand Oaks, CA, USA: SAGE Publications, 2014.
- [45] Y. Wahyuni, “Identifikasi gaya belajar mahasiswa pendidikan matematika Universitas Bung Hatta [Identification of learning styles of mathematics education students at Bung Hatta University],” Jurnal Penelitian dan Pembelajaran Matematika, vol. 10, no. 2, pp. 128–132, 2017, doi: 10.30870/jppm.v10i2.2045.
- [46] R. R. Hake, “Interactive-engagement versus traditional methods: A six-thousand-student survey of mechanics test data for introductory physics courses,” Am. J. Phys., vol. 66, no. 1, pp. 64–74, 1998, doi: 10.1119/1.18809.
- [47] S. Audina, D. S. Nahdi, and S. Sudianto, “Analisis pemahaman konsep matematis siswa pada operasi penjumlahan bilangan bulat menggunakan media garis bilangan [Analysis of students' understanding of mathematical concepts in the operation of adding integers using number lines as media],” Polinomial: Jurnal Pendidikan Matematika, vol. 2, no. 1, pp. 11–17, 2023, doi: 10.56916/jp.v2i1.305.
- [48] S. S. Shapiro and M. B. Wilk, “An analysis of variance test for normality (complete samples),” Biometrika, vol. 52, no. 3/4, pp. 591–611, 1965, doi: 10.2307/2333709.
- [49] M. B. Brown and A. B. Forsythe, “Robust tests for the equality of variances,” J. Am. Stat. Assoc., vol. 69, no. 346, pp. 364–367, 1974, doi: 10.1080/01621459.1974.10482955.
- [50] S. le Cessie, J. J. Goeman, and O. M. Dekkers, "Who is afraid of non-normal data? Choosing between parametric and non-parametric tests," Eur. J. Endocrinol., vol. 182, no. 2, pp. E1–E3, 2020, doi: 10.1530/EJE-19-0922.
- [51] S. Sudjana, Metoda Statistika [Statistical Methods], Bandung, Indonesia: Tarsito, 2005.
- [52] Z. Drezner and O. Turel, “Normalizing variables with too-large kurtosis: A study of the effect on the Mann-Whitney U test,” Commun. Stat. Simul. Comput., vol. 40, no. 10, pp. 1524–1536, 2011, doi: 10.1080/03610918.2011.594534.
- [53] J. Cohen, Statistical Power Analysis for the Behavioral Sciences, 2nd ed. Hillsdale, NJ, USA: Lawrence Erlbaum Associates, 1988.
- [54] A. Bakker, J. Cai, L. English, G. Kaiser, V. Mesa, and W. Van Dooren, “Beyond small, medium, or large: Points of consideration when interpreting effect sizes,” Educ. Stud. Math., vol. 102, no. 1, pp. 1–8, 2019, doi: 10.1007/s10649-019-09908-4.
- [55] M. A. Kraft, “Interpreting effect sizes of education interventions,” Educ. Res., vol. 49, no. 4, pp. 241–253, 2020, doi: 10.3102/0013189X20912798.
- [56] H. W. Marsh, K.-T. Hau, and Z. Wen, “In search of golden rules: Comment on hypothesis-testing approaches to setting cutoff values for fit indexes and dangers in overgeneralizing Hu and Bentler’s (1999) findings,” Struct. Equ. Modeling, vol. 11, no. 3, pp. 320–341, 2004, doi: 10.1207/s15328007sem1103_2.
- [57] S. Sunarti, “Peningkatan hasil belajar siswa pada mata pelajaran matematika dengan menggunakan metode pembelajaran matematika gasing di sekolah dasar [Improving student learning outcomes in mathematics through the use of the 'Gasing' mathematics learning method in elementary schools],” TANGGAP: Jurnal Riset dan Inovasi Pendidikan Dasar, vol. 2, no. 1, pp. 29–38, 2021, doi: 10.55933/tjripd.v2i1.263.
- [58] L. F. Hidayah, W. Sutriyani, and E. Zumrotun, “Efektivitas metode gasing berbantuan media uno pintar (untar) terhadap hasil belajar matematika [The effectiveness of the Gasing method, supported by 'Uno Pintar' (Untar) media, on mathematics learning outcomes],” AKSIOMA: Jurnal Matematika dan Pendidikan Matematika, vol. 15, no. 3, pp. 444–454, 2024, doi: 10.26877/aks.v15i3.19766.
- [59] M. Firdaus and Mukhtar, “Reconstructing multivariable calculus learning through mathematical discourse for conceptual and procedural understanding,” Journal Evaluation in Education (JEE), vol. 6, no. 1, pp. 45–54, 2025, doi: 10.37251/jee.v6i1.1327.
- [60] L. S. Vygotsky, Mind in Society: The Development of Higher Psychological Processes. Cambridge, MA, USA: Harvard University Press, 1978.
- [61] S. Ebner, M. K. MacDonald, P. Grekov, and K. B. Aspiranti, “A meta-analytic review of the concrete-representational-abstract math approach,” Learn. Disabil. Res. Pract., vol. 40, no. 1, pp. 31–42, 2025, doi: 10.1177/09388982241292299.
- [62] S. K. Prosser and S. F. Bismarck, “Concrete–representational–abstract (CRA) instructional approach in an Algebra I inclusion class: Knowledge retention versus students’ perception,” Educ. Sci., vol. 13, no. 10, p. 1061, 2023, doi: 10.3390/educsci13101061.
- [63] N. A. Harun, K. G. Cuevas, O. Asakil, J. Alviar, and L. J. Solon, “Assessing students’ mastery and misconceptions in the fundamental operations on integers,” International Journal of Science, Technology, Engineering and Mathematics, vol. 3, no. 3, pp. 36–55, 2023, doi: 10.53378/353000.
- [64] H. Hermansyah, I. Aras, and J. B. Darmayasa, “Pembelajaran operasi penjumlahan dan pengurangan bilangan bulat menggunakan garis bilangan,” Jurnal Pendidikan Matematika dan Ilmu Pengetahuan Alam, vol. 9, no. 1, pp. 13–28, 2021, doi: 10.37058/jpm-ipa.v9i1.2645.
- [65] K. R. Koedinger and M. W. Alibali, “The relationship between conceptual and procedural knowledge: A review,” in Handbook of Research on Mathematics Teaching and Learning, D. A. Grouws, Ed. Charlotte, NC, USA: Information Age Publishing, 2007, pp. 207–223.
- [66] B. Rittle-Johnson, E. R. Fyfe, and A. M. Loehr, “Improving conceptual and procedural knowledge: The impact of instructional content within a mathematics lesson,” Br. J. Educ. Psychol., vol. 86, no. 4, pp. 576–591, 2016, doi: 10.1111/bjep.12124.
- [67] E. A. Silver, “Fostering creativity through instruction rich in mathematical problem solving and problem posing,” ZDM, vol. 29, no. 3, pp. 75–80, 1997, doi: 10.1007/s11858-997-0003-x.
- [68] Y. Surya, Modul Pelatihan Matematika GASING SD: Bagian 1 [GASING Elementary School Mathematics Training Module: Part 1]. Tangerang, Indonesia: PT Kandel, 2013.
- [69] E. L. Thorndike, The Fundamentals of Learning. New York, NY, USA: Teachers College, Columbia University, 1932.
- [70] L. W. Santrock, Educational Psychology, 6th ed. New York, NY, USA: McGraw-Hill Education, 2017.
- [71] D. H. Jonassen and B. L. Grabowski, Handbook of Individual Differences, Learning, and Instruction. Hillsdale, NJ, USA: Lawrence Erlbaum Associates, 1993.
- [72] H. Pashler, M. McDaniel, D. Rohrer, and R. Bjork, “Learning styles: Concepts and evidence,” Psychol. Sci. Public Interest, vol. 9, no. 3, pp. 105–119, 2008, doi: 10.1111/j.1539-6053.2009.01038.x.
- [73] B. A. Rogowsky, B. M. Calhoun, and P. Tallal, “Matching learning style to instructional method: Effects on comprehension,” J. Educ. Psychol., vol. 107, no. 1, pp. 64–78, 2015, doi: 10.1037/a0037478.
- [74] B. A. Rogowsky, B. M. Calhoun, and P. Tallal, “Providing instruction based on students’ learning style preferences does not improve learning,” Front. Psychol., vol. 11, p. 164, 2020, doi: 10.3389/fpsyg.2020.00164.
- [75] D. D. Hariri, H. Mahmudah, F. S. Wibawa, and N. Kania, “Unraveling the connection: A systematic review of learning styles and mathematics achievement,” Pedagogical Research, vol. 10, no. 1, p. em0232, 2025, doi: 10.29333/pr/15681.
- [76] R. Rusman, Model-Model Pembelajaran: Mengembangkan Profesionalisme Guru, 4th ed [Learning Models: Developing Teacher Professionalism, 4th ed]. Jakarta, Indonesia: Rajawali Pers, 2017.
- [77] A. Retnawati, H. Hadi, and A. C. Nugraha, “Vocational high school teachers’ difficulties in implementing the assessment in curriculum 2013 in Yogyakarta province of Indonesia,” Int. J. Instr., vol. 9, no. 1, pp. 33–48, 2016, doi: 10.12973/iji.2016.913a.
- [78] M. Swan, “The impact of task-based professional development on teachers’ practices and beliefs: A design research study,” J. Math. Teach. Educ., vol. 10, no. 4–6, pp. 217–237, 2007, doi: 10.1007/s10857-007-9038-8.