Ergonomics of Computer Workstation

  • Pranab Kumar Nag
Part of the Design Science and Innovation book series (DSI)


Office goers have been compelled to or increasingly constrained to remain seated in a chair–desk complex. Assessment of seat dynamics and user-seat compatibility has been examined, using approaches such as anthropometric, biomechanical, electromyographic and stabilometric analysis, comfort rating and materials construction. This chapter describes biomechanics of sitting, analysis of sitting modes and seated features, and aspects of Balans chairs. Further, it elaborates the ergo-design characteristics of an office chair, including different chair tilting mechanisms. Methodological details of the simulated seat–desk system are included for human–seat–desk interface analysis, covering the effects of the slope of the seat pan, backrest angles, height of armrest, upright and slouch sitting, about body force distribution and muscle activation. Several general risk factors, such as seating system, repetitive use of keyboards/mouse, chair–desk with or without adjustable armrests, supported/unsupported forearm and wrist, are all interconnected and compelling components of workplace constraints in computer work. Discussion includes options of good job design, periodic task rotation, rest breaks, stretching exercises in relieving the physical and mental strain of computer operators.


  1. Aarås, A., Horgen, G., Bjørset, H. H., Ro, O., & Thoresen, M. (1998). Musculoskeletal, visual and psychosocial stress in VDU operators before and after multidisciplinary ergonomic interventions. Applied Ergonomics, 29(5), 335–354.CrossRefGoogle Scholar
  2. Aarås, A., Horgen, G., Bjørset, H. H., Ro, O., & Walsøe, H. (2001). Musculoskeletal, visual and psychosocial stress in VDU operators before and after multidisciplinary ergonomic interventions. A 6 years prospective study—Part II. Applied Ergonomics, 32(6), 559–571.CrossRefGoogle Scholar
  3. Adams, M. A., & Dolan, P. (2005). Spine biomechanics. Journal of Biomechanics, 38(10), 1972–1983.CrossRefGoogle Scholar
  4. Albin, T. (1997). Effect of wrist rest use and keyboard tilt on wrist angle while keying. In 13th Triennial Conference of the International Ergonomics Association, Vol. 1.Google Scholar
  5. Albin, T. J. (2014). Dissertation, Industrial and Management Systems Engineering, University of Nebraska, Lincoln.Google Scholar
  6. Alexander, L. A., Hancock, E., Agouris, I., Smith, F. W., & MacSween, A. (2007). The response of the nucleus pulposus of the lumbar intervertebral discs to functionally loaded positions. Spine, 32, 1508–1512.CrossRefGoogle Scholar
  7. Amick, B. C., III, Menendez, C. C., Bazzani, L., Robertson, M., DeRango, K., Rooney, T., et al. (2012). A field intervention examining the impact of an office ergonomics training and a highly adjustable chair on visual symptoms in a public sector organization. Applied Ergonomics, 43, 625–631.CrossRefGoogle Scholar
  8. ANSI. (1988). American national standard for human factors engineering of visual display terminal workstations. Santa Monica, California: The Human Factors Society.Google Scholar
  9. Babski-Reeves, K., Stanfield, J., & Hughes, L. (2005). Assessment of video display workstation set up on risk factors associated with the development of low back and neck discomfort. International Journal of Industrial Ergonomics, 35(7), 593–604.CrossRefGoogle Scholar
  10. Beach, T. A., McDonald, K. A., Coke, S. K., & Callaghan, J. P. (2008). Gender responses to automobile and office sitting—influence of hip, hamstring, and low-back flexibility on seated postures. The Open Ergonomics Journal, 1, 1–9.CrossRefGoogle Scholar
  11. Been, E., & Kalichman, L. (2014). Lumbar lordosis. The Spine Journal: Official Journal of the North American Spine Society, 14, 87–97.CrossRefGoogle Scholar
  12. Bendix, T., Krohn, I., Jessen, F., & Aaras, A. (1985). Trunk posture and trapezius muscle load while working in standing supported-standing and sitting positions. Spine, 10, 433–439.CrossRefGoogle Scholar
  13. Bendix, T., Poulsen, V., Klausen, K., & Jensen, C. V. (1996). What does a backrest actually do to the lumbar spine? Ergonomics, 39, 533–542.CrossRefGoogle Scholar
  14. Brodeur, R. R., & Reynolds, H. M. (1990). Passive mechanics of the lumbo-pelvic spine for erect and slumped seated postures. In Proceedings of the 1990 International Conference on Spinal Manipulation (pp. 190–193). FCER: Arlington, Virginia.Google Scholar
  15. Callaghan, J. P., & McGill, S. M. (2001a). Intervertebral disc herniation: Studies on a porcine model exposed to highly repetitive flexion/extension motion with compressive force. Clinical Biomechanics, 16, 28–37.CrossRefGoogle Scholar
  16. Callaghan, J. P., & McGill, S. M. (2001b). Low back joint loading and kinematics during standing and unsupported sitting. Ergonomics, 44, 280–294.CrossRefGoogle Scholar
  17. Callaghan, J. (2006). The impact of T1-L5 Free Shoulders (R) backrest on prolonged seated work. Prepared for Keilhauer, Toronto, Ontario, Canada.Google Scholar
  18. Callaghan, J. P., & Dunk, N. M. (2002). Examination of the exion relaxation phenomenon in erector spine muscles during short duration slumped sitting. Clinical Biomechanics, 17, 353–360.CrossRefGoogle Scholar
  19. Chiari, L., Rocchi, L., & Cappello, A. (2002). Stabilometric parameters are affected by anthropometry and foot placement. Clinical Biomechanics, 17, 666–677.CrossRefGoogle Scholar
  20. Clemes, S. A., O’Connell, S. E., & Edwardson, C. L. (2014). Office workers’ objectively measured sedentary behavior and physical activity during and outside working hours. Journal of Occupational and Environmental Medicine, 56, 298–303.CrossRefGoogle Scholar
  21. Cobb, T., An, K., & Cooney, W. (1995). Externally applied forces to the palm increase carpal tunnel pressure. American Journal of Hand Surgery, 20(2), 181–185.CrossRefGoogle Scholar
  22. Colombini, D., Occhipinti, E., Frigo, C., Pedotti, A., & Grieco, A. (1985). Biomechanical, electromyographical and radiological study of seated postures. In Proceedings of the First International Occupational Ergonomics Symposium. Taylor and Francis: London, Zadar, Yugoslavia.Google Scholar
  23. Cook, C., & Burgess-Limerick, R. (2002). Forearm support for intensive computer users: A field study. In Paper presented at the HF 2002 Human Factors Conference, Melbourne, Australia.Google Scholar
  24. Cook, C., Burgess-Limerick, R., & Papalia, S. (2004a). The effect of upper extremity posture and muscle activity during keyboard use. Applied Ergonomics, 35, 285–292.CrossRefGoogle Scholar
  25. Cook, C., Burgess-Limerick, R., & Papalia, S. (2004b). The effect of wrist rests and forearm support during keyboard and mouse use. International Journal of Industrial Ergonomics, 33(5), 463–472.CrossRefGoogle Scholar
  26. Corlett, E. N. (1999). Are you sitting comfortably? International Journal Industrial Ergonomics, 24, 7–12.CrossRefGoogle Scholar
  27. Dankaerts, W., O’Sullivan, P., Burnett, A., & Straker, L. (2006). Altered patterns of superficial trunk muscle activation during sitting in nonspecific chronic low back pain patients: Importance of subclassification. Spine, 31, 2017–2023.CrossRefGoogle Scholar
  28. De Carvalho, D. E., & Callaghan, J. P. (2012). Influence of automobile seat lumbar support prominence on spine and pelvic postures: a radiological investigation. Applied Ergonomics, 43, 876–882.CrossRefGoogle Scholar
  29. Dickerson, O. B., & Erdil, M. (1999). Video display workstations and cumulative trauma disorders. In M. Erdil, & O. B. Dickerson (Eds.), Chap. 10 in Cumulative trauma disorders. Prevention, evaluation and treatment (pp. 251–269). New York: Van Nostrand Reinhold.Google Scholar
  30. Dolan, P., & Adams, M. A. (2001). Recent advances in lumbar spinal mechanics and their significances for modeling. Clinical Biomechanics, 16, S8–S16.CrossRefGoogle Scholar
  31. Drury, C. G., & Hoffmann, E. R. (1992). A model for movement time on data entry keyboards. Ergonomics, 16, 41–47.Google Scholar
  32. Dunk, N. M., & Callaghan, J. P. (2010). Lumbar spine movement patterns during prolonged sitting differentiate low back pain developers from matched asymptomatic controls. Work (Reading, Mass.) 35, 3–14.Google Scholar
  33. Dvorak, A., & Dealey, W. L. (1936). Typewriter keyboard. U.S. Patent No. 2,040,248. 12 May 1936.Google Scholar
  34. Eklof, M., Ingelgard, A., & Hagberg, M. (2004). Is participative ergonomics associated with better working environment and health? A study among Swedish white-collar VDU users. International Journal of Industrial Ergonomics, 34, 355–366.CrossRefGoogle Scholar
  35. Eklund, J., & Liew, M. (1991). Evaluation of seating: The influence of hip and knee angles on spinal posture. International Journal of Industrial Ergonomics, 8, 67–73.CrossRefGoogle Scholar
  36. Ericson, O., & Goldie, I. (1989). Spinal shrinkage with three different types of chair whilst performing video display unit work. International Journal of Industrial Ergonomics, 3, 177–183.CrossRefGoogle Scholar
  37. Fagarasanu, M., Kumar, S., & Narayan, Y. (2005). The training effect on typing on two alternative keyboards. International Journal of Industrial Ergonomics, 35, 509–516.CrossRefGoogle Scholar
  38. Fenety, A., & Walker, J. M. (2002). Short-term effects of workstation exercises on musculoskeletal discomfort and postural changes in seated video display unit workers. Physical Therapy, 82(6), 578–589.Google Scholar
  39. Fenety, A., Putnam, C., & Walker, J. M. (2000). In-chair movement: Validity, reliability and implications for measuring sitting discomfort. Applied Ergonomics, 31, 383–393.CrossRefGoogle Scholar
  40. Frey, J. K., & Tecklin, J. S. (1986). Comparison of lumbar curves when sitting on the Westnofa Balans Multi-Chair, sitting on a conventional chair, and standing. Physical Therapy, 66, 1365–1369.CrossRefGoogle Scholar
  41. Gedalia, U., Solomonow, M., Zhou, B. H., Baratta, R. V., Lu, Y., & Harris, M. (1999). Biomechanics of increased exposure to lumbar injury caused by cyclic loading: Part 2. Recovery of reflexive muscular stability with rest. Spine, 24(23), 2461.CrossRefGoogle Scholar
  42. Gilad, I., & Harel, S. (2000). Muscular effort in four keyboard designs. International Journal of Industrial Ergonomics, 26, 1–7.CrossRefGoogle Scholar
  43. Grandjean, E. (1978). Report on the present state of knowledge in the area of ergonomic keyboard design. Institute for Hygiene and Industrial Physiology, Swiss Technical College, Zurich.Google Scholar
  44. Grandjean, E., Hunting, W., & Piderman, M. (1983). VDT workstation design: Preferred settings and their effects. Human Factors, 25, 161–175.CrossRefGoogle Scholar
  45. Green, R. A., Briggs, C. A., & Wrigley, T. V. (1991). Factors related to working posture and its assessment among keyboard operators. Applied Ergonomics, 22, 29–35.CrossRefGoogle Scholar
  46. Grondin, D. E., Triano, J. J., Steven, T., & Soave, D. (2013). The effect of a lumbar support pillow on lumbar posture and comfort during a prolonged seated task. Chiropractic & Manual Therapies, 21, 21.CrossRefGoogle Scholar
  47. Gustafsson, E., & Hagberg, M. (2003). Computer mouse use in two different hand position: Exposure, comfort, exertion and productivity. Applied Ergonomics, 34, 107–113.CrossRefGoogle Scholar
  48. Hedge, A., & Powers, J. (1995). Wrist postures while keyboarding: Effects of a negative slope keyboard system and full motion forearm supports. Ergonomics, 38(3), 508–517.CrossRefGoogle Scholar
  49. Hedge, A. (1994). Effect of a negative slope keyboard system on musculoskeletal complaints among computer workers. In Proceedings of the 12th Triennial Congress of the International Ergonomics Association (pp. 462–466).Google Scholar
  50. Hedge, A., Mc Crobic, D., Morimoto, S., Rodriguez, S., & Land, B. (1995). Toward plain-free computing. Ergonomics in Design, 4(1), 4–10.CrossRefGoogle Scholar
  51. Helander, M. G., & Quance, L. A. (1990). Effect of work-rest schedules on spinal shrinkage in the sedentary worker. Applied Ergonomics, 21, 279–284.CrossRefGoogle Scholar
  52. Helander, M. G., & Zhang, L. (1997). Field studies of comfort and discomfort in sitting. Ergonomics, 40, 895–915.CrossRefGoogle Scholar
  53. Henning, R. A., Jacques, P., Kissel, G. V., Sullivan, A. B., & Alteras-Webb, S. M. (1997). Frequent short rest breaks from computer work: Effects on productivity and well-being at two field sites. Ergonomics, 40, 78–91.CrossRefGoogle Scholar
  54. Jans, M. P., Proper, K. I., & Hildebrandt, V. H. (2007). Sedentary behavior in Dutch workers: Differences between occupations and business sectors. American Journal of Preventive Medicine, 33, 450–454.CrossRefGoogle Scholar
  55. Jaschinski- Kruza, W. (1990). On the preferred distances to screen and document at VDU workplaces. Ergonomics, 33, 1055–1063.CrossRefGoogle Scholar
  56. Keegan, J. J. (1953). Alterations of the lumbar curve related to posture and seating. The Journal of Bone and Joint Surgery, 35-A, 589–603.Google Scholar
  57. Kingma, I., & van Dieen, J. H. (2009). Static and dynamic postural loadings during computer work in females: Sitting on an office chair versus sitting on an exercise ball. Applied Ergonomics, 40, 199–205.CrossRefGoogle Scholar
  58. Klockenberg, E. A. (1926). Rationalization of the typewriter and of its use (in German). Berlin: Springer.Google Scholar
  59. Lee, E. S., Ko, C. W., Suh, S. W., Kumar, S., Kang, I. K., & Yang, J. H. (2014). The effect of age on sagittal plane profile of the lumbar spine according to standing, supine, and various sitting positions. Journal of Orthopaedic Surgery and Research, 9(1), 11.CrossRefGoogle Scholar
  60. Leivseth, G., & Drerup, B. (1997). Spinal shrinkage during work in a sitting posture compared to work in a standing posture. Clinical Biomechanics, 12, 409–418.CrossRefGoogle Scholar
  61. Lengsfeld, M., Frank, A., van Deursen, D. L., & Griss, P. (2000a). Lumbar spine curvature during office chair sitting. Medical Engineering and Physics, 22(9), 665–669.CrossRefGoogle Scholar
  62. Lengsfeld, M., van Deursen, D. L., Rohlmann, A., van Deursen, L. L. J. M., & Griss, P. (2000b). Spinal load changes during rotatory dynamic sitting. Clinical Biomechanics, 15, 295–297.CrossRefGoogle Scholar
  63. Liebowitz, S. J., & Margolis, S. E. (1990). The fable of the keys. The Journal of Law and Economics, 33(1), 1–25.CrossRefGoogle Scholar
  64. Link, C. S., Nicholson, G. G., Shaddeau, S. A., Birch, R., & Gossman, M. R. (1990). Lumbar curvature in standing and sitting in two types of chairs: Relationship of hamstring and hip flexor muscle length. Physical Therapy, 70, 611–618.CrossRefGoogle Scholar
  65. Mahmud, N., Kenny, D. T., Zein, R. M., & Hassan, S. N. (2011). Ergonomic training reduces musculoskeletal disorders among office workers: Results from the 6-month follow-up. The Malaysian Journal of Medical Sciences, 18(2), 16.Google Scholar
  66. Makhsous, M., Lin, F., Hendrix, R. W., Hepler, M., & Zhang, L. Q. (2003). Sitting with adjustable ischial and back supports: Biomechanical changes. Spine, 28(11), 1113–1121.Google Scholar
  67. Mandal, A. C. (1985). The seated man: Homo sedans. Denmark: Dafnia Publications.Google Scholar
  68. McGill, S. M., & Fenwick, C. M. (2009). Using a pneumatic support to correct sitting posture for prolonged periods: A study using airline seats. Ergonomics, 52(9), 1162–1168.CrossRefGoogle Scholar
  69. McGill, S. M. (2004). Linking latest knowledge of injury mechanisms and spine function to the prevention of low back disorders. Journal of Electromyography and Kinesiology, 14, 43–47.CrossRefGoogle Scholar
  70. McGill, S. M., Kavcic, N. S., & Harvey, E. (2006). Sitting on a chair or an exercise ball: Various perspectives to guide decision making. Clinical Biomechanics, 21(4), 353–360.CrossRefGoogle Scholar
  71. Mörl, F., & Bradl, I. (2013). Lumbar posture and muscular activity while sitting during office work. Journal of Electromyography and Kinesiology, 23(2), 362–368.CrossRefGoogle Scholar
  72. Mueller, G. F., & Hassenzahl, M. (2010). Sitting comfort of ergonomic office chairs—developed versus intuitive evaluation. International Journal of Occupational Safety and Ergonomics, 16(3), 369–374.CrossRefGoogle Scholar
  73. Nag, P. K., Pal, S., Kotadiya, S. M., Nag, A., & Gosai, K. (2008). Human–seat interface analysis of upper and lower body weight distribution. International Journal of Industrial Ergonomics, 38(5), 539–545.CrossRefGoogle Scholar
  74. Nag, P. K., Pal, S., Nag, A., & Vyas, H. (2009). Influence of arm and wrist support on forearm and back muscle activity in computer keyboard operation. Applied Ergonomics, 40(2), 286–291.CrossRefGoogle Scholar
  75. Nag, P. K., & Pal, S. (2008). Musculo-skeletal risk factors among computer keyboard users. In G. Jayakumar, & M. Retneswari (Eds.), Occupational Health for health care professionals (pp. 195–207). Malayasin Medical Association: Kuala Lumpur.Google Scholar
  76. Nakaseko, M., Grandjean, E., Hüunting, W., & Gierer, R. (1985). Studies on ergonomically designed alphanumeric keyboards. Human Factors, 27(2), 175–187.CrossRefGoogle Scholar
  77. O’Sullivan, P. B., Burnett, A., Floyd, A. N., Gadsdon, K., Logiudice, J., Miller, D., et al. (2003). Lumbar repositioning deficit in a specific low back pain population. Spine, 28(10), 1074–1079.CrossRefGoogle Scholar
  78. O’Sullivan, K., O’Dea, P., Dankaerts, W., O’Sullivan, P., Clifford, A., & O’Sullivan, L. (2010). Neutral lumbar spine sitting posture in pain-free subjects. Manual Therapy, 15(6), 557–561.CrossRefGoogle Scholar
  79. Parsons, C. (1991). Use of wrist rest by data input VDU operators. In Contemporary Ergonomics. Proceedings of the Ergonomic Society.Google Scholar
  80. Pope, M. H., Goh, K. L., & Magnusson, M. L. (2002). Spine ergonomics. Annual Review of Biomedical Engineering, 4(1), 49–68.CrossRefGoogle Scholar
  81. Pynt, J. (2015). Rethinking design parameters in the search for optimal dynamic seating. Journal of Bodywork and Movement Therapies, 19(2), 291–303.CrossRefGoogle Scholar
  82. Rocchi, L., Chiari, L., & Cappello, A. (2004). Feature selection of stabilometric parameters based on principal component analysis. Medical & Biological Engineering & Computing, 42(1), 71–79.CrossRefGoogle Scholar
  83. Rohlmann, A., Arntz, U., Graichen, F., & Bergmann, G. (2001). Loads on an internal spinal fixation device during sitting. Journal of Biomechanics, 34(8), 989–993.CrossRefGoogle Scholar
  84. Rohlmann, A., Consmüller, T., Dreischarf, M., Bashkuev, M., Disch, A., Pries, E., et al. (2014). Measurement of the number of lumbar spinal movements in the sagittal plane in a 24-hour period. European Spine Journal, 23(11), 2375–2384.CrossRefGoogle Scholar
  85. Sánchez-Zuriaga, D., Adams, M. A., & Dolan, P. (2010). Is activation of the back muscles impaired by creep or muscle fatigue? Spine, 35(5), 517–525.CrossRefGoogle Scholar
  86. Sandfeld, J., & Jensen, B. R. (2005). Effect of computer mouse gain and visual demand on mouse clicking performance and muscle activation in a young and elderly group of experienced computer users. Applied Ergonomics, 36(5), 547–555.CrossRefGoogle Scholar
  87. Scarvelis, D., & Wells, P. S. (2006). Diagnosis and treatment of deep-vein thrombosis. Canadian Medical Association Journal, 175(9), 1087–1092.CrossRefGoogle Scholar
  88. Serina, E. R., Tal, R., & Rempel, D. (1999). Wrist and forearm postures and motions during typing. Ergonomics, 42(7), 938–951.CrossRefGoogle Scholar
  89. Shenoy, S., & Aruin, A. S. (2007). Effect of chair design on feed-forward postural control in sitting. Motor Control, 11(4), 309–321.CrossRefGoogle Scholar
  90. Simoneau, G. G., & Marklin, R. W. (2001). Effect of computer keyboard slope and height on wrist extension angle. Human Factors, 43(2), 287–298.CrossRefGoogle Scholar
  91. Simoneau, G. G., Marklin, R. W., & Berman, J. E. (2003). Effect of computer keyboard slope on wrist position and forearm electromyography of typists without musculoskeletal disorders. Physical Therapy, 83(9), 816–830.Google Scholar
  92. Smith, M. J., Karsh, B. T., Conway, F. T., Cohen, W. J., James, C. A., Morgan, J. J., et al. (1998). Effects of a split keyboard design and wrist rest on performance, posture, and comfort. Human Factors, 40(2), 324–336.CrossRefGoogle Scholar
  93. Solomonow, M., Baratta, R. V., Banks, A., Freudenberger, C., & Zhou, B. H. (2003a). Flexion–relaxation response to static lumbar flexion in males and females. Clinical Biomechanics, 18(4), 273–279.CrossRefGoogle Scholar
  94. Solomonow, M., Baratta, R. V., Zhou, B. H., Burger, E., Zieske, A., & Gedalia, A. (2003b). Muscular dysfunction elicited by creep of lumbar viscoelastic tissue. Journal of Electromyography and Kinesiology, 13(4), 381–396.CrossRefGoogle Scholar
  95. Starr, S. J., Shute, S. J., & Thompson, C. R. (1985). Relating posture to discomfort in VDT use. Journal of Occupational and Environmental Medicine, 27(4), 269–271.Google Scholar
  96. Szeto, G. P., Straker, L. M., & O’Sullivan, P. B. (2005). The effects of typing speed and force on motor control in symptomatic and asymptomatic office workers. International Journal of Industrial Ergonomics, 35(9), 779–795.CrossRefGoogle Scholar
  97. Tepper, M., Vollenbroek-Hutten, M. M. R., Hermens, H. J., & Baten, C. T. M. (2003). The effect of an ergonomic computer device on muscle activity of the upper trapezius muscle during typing. Applied Ergonomics, 34(2), 125–130.CrossRefGoogle Scholar
  98. Tittiranonda, P., Burastero, S., & Rempel, D. (1999). Risk factors for musculoskeletal disorders among computer users. Ooccupational Medicine, 14, 17–38.Google Scholar
  99. Tittiranonda, P., Rempel, D., Armstrong, T., & Burastero, S. (2000). Effect of four computer keyboards in computer users with upper extremity musculoskeletal disorders. In Proceedings of the Human Factors and Ergonomics Society Annual Meeting (Vol. 44, No. 6, pp. 692–695). Sage CA: Los Angeles, CA: SAGE Publications.Google Scholar
  100. Van Deursen, D. L., Van Deursen, L. L. J. M., Snijders, C. J., & Goossens, R. H. M. (2000). Effect of continuous rotary seat pan movements on physiological oedema of the lower extremities during prolonged sitting. International Journal of Industrial Ergonomics, 26(5), 521–526.CrossRefGoogle Scholar
  101. Wilke, H. J., Neef, P., Caimi, M., Hoogland, T., & Claes, L. E. (1999). New in vivo measurements of pressures in the intervertebral disc in daily life. Spine, 24(8), 755–762.CrossRefGoogle Scholar
  102. Youdas, J. W., Hollman, J. H., & Krause, D. A. (2006). The effects of gender, age, and body mass index on standing lumbar curvature in persons without current low back pain. Physiotherapy Theory and Practice, 22(5), 229–237.CrossRefGoogle Scholar

Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Pranab Kumar Nag
    • 1
  1. 1.School of Environment and Disaster ManagementRamakrishna Mission Vivekananda UniversityKolkataIndia

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