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Plastic Materials

  • Bert Björkner

Abstract

The polymer industry is now one of the most important branches of the chemical industry and uses a wider variety of chemicals than any other. The number of commercially important plastics today is around 50. Application areas for plastics are many and varied; the construction industry, packaging, electronics, recreation, medical, etc. Of the base plastics, 30% are used for packaging and 20% in the construction industry.

Keywords

Contact Dermatitis Allergic Contact Dermatitis Unsaturated Polyester Contact Allergy Unsaturated Polyester Resin 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    Dahlquist I, Fregert S, Trulsson L (1983) Contact allergy to trimethylolpropane triacrylate ( TMPTA) in an aziridine plastic hardener. Contact Dermatitis 9: 122–124Google Scholar
  2. 2.
    Cofield BG, Storrs FJ, Strawn CB (1985) Contact allergy to aziridine paint hardener. Arch Dermatol 121: 373–376PubMedGoogle Scholar
  3. 3.
    Dempsey KJ (1982) Hypersensitivity to Sta-Lok and Loctite anaerobic sealants. J Am Acad Dermatol 7: 779–784PubMedGoogle Scholar
  4. 4.
    Ranchoff RE, Taylor JS (1985) Contact dermatitis to anaerobic sealants. J Am Acad Dermatol 13: 1015–1020PubMedGoogle Scholar
  5. 5.
    Conde’-Salazar L, Guimaraens D, Romero LV (1988) Occupational allergic contact dermatitis from anaerobic acrylic sealants. Contact Dermtitis 18: 129–132Google Scholar
  6. 6.
    Van der Walle HB (1982) Sensitizing potential of acrylic monomers in guinea pig. Thesis, Catholic University of NijmegenGoogle Scholar
  7. 7.
    Van der Walle HB, Clecak G, Geleick H, Bensink T (1982) Sensitizing potential of 15 mono(meth)acrylates in the guinea pig. Contact Dermatitis 8: 223–235PubMedGoogle Scholar
  8. 8.
    Van der Walle HB, Waegemaekers T, Bensink (1983) Sensitizing potential of 12 di(meth)acrylates in the guinea pig. Contact Dermatitis 9: 10–20Google Scholar
  9. 9.
    Waegemaekers T (1985) Some toxicological aspects of acrylic monomers, notably with reference to the skin. Thesis, Katholieke Universiteit to NijmegenGoogle Scholar
  10. 10.
    Cavelier C, Jelen G, Herve-Bazin B, Fossereau J (1981) Irritation et allergic aux acrylates et methacrylates. Premiere partie. Monoacrylates et monomethacrylates simples. Ann Dermatol Venereol 108: 549–556Google Scholar
  11. 11.
    Björkner B (1984) Sensitizing capacity of ultraviolet curable acrylic compounds. Thesis, University of LundGoogle Scholar
  12. 12.
    Beurey J, Mougeolle J-M, Weber M (1976) Accidents cutanés des résines acryliques dans l’imprimerie. Ann Dermatol Syphiligr 103: 423–430Google Scholar
  13. 13.
    Malten KE, den Arend JACJ, Wiggers RE (1979) Delayed irritation: hexanediol diacrylate and butanediol diacrylate. Contact Dermatitis 5: 178–184PubMedGoogle Scholar
  14. 14.
    Nethercott JR, Gupta S, Rosen C„ Enders LJ, Pilger CW (1984) Tetraethylene glycol diacrylate. A cause of delayed cutaneous irritant reaction and allergic contact dermatitis. J Occup Med 26: 513–516Google Scholar
  15. 15.
    Parker D, Turk JL (1983) Contact sensitivity to acrylate compounds in guinea pigs. Contact Dermatitis 9: 55–60PubMedGoogle Scholar
  16. 16.
    Björkner B (1981) Sensitization capacity of acrylated prepolymers in ultraviolet curing inks tested in the guinea pig. Accta Derm Venereol (Stockh) 61: 7–10Google Scholar
  17. 17.
    Björkner B, Niklasson B, Persson K (1984) The sensitizing potential of di(meth)acrylates based on bisphenol A or epoxy resin in the guinea pig. Contact Dermatitis 10: 286–304PubMedGoogle Scholar
  18. 18.
    Björkner B (1982) Sensitization capacity of polyester methacrylate in ultraviolet curing inks tested in the guinea pig. Acta Derm Venereol 62: 153–182PubMedGoogle Scholar
  19. 19.
    Björkner B (1984) Sensitizing potential of urethane (meth)acrylates in the guinea pig. Contact Dermatitis 11: 115–119PubMedGoogle Scholar
  20. 20.
    Nethercott JR, Jakubovic HR, Pilger C, Smith JW (1982) Allergic contact dermatitis due to urethane acrylate in ultraviolet cured inks. Br J Ind Med 40: 241–250Google Scholar
  21. 21.
    Bang Pedersen N, Senning A, Otkjaer Nielsen A (1983) Different sensitizing acrylic monomers in NAPP printing plate. Contact Dermatitis 9: 459–464PubMedGoogle Scholar
  22. 22.
    Björkner B (1984) Contact allergy to 2-hydroxypropyl methacrylate (2-HPMA) in an ultraviolet curable ink. Acta Derm Venereol (Stockh) 64: 264–267Google Scholar
  23. 23.
    Malten KE, Bende WJM (1979) 2-Hydroxy-ethyl-methacrylate and di-and tetraethylene glycol dimethacrylate: contact sensitizers in a photoprepolymer printing plate procedure. Contact Dermatitis 5: 214–220Google Scholar
  24. 24.
    Whittington CW (1981) Dermatitis from UV acrylate in adhesive. Contact Dermatitis 7: 203–204PubMedGoogle Scholar
  25. 25.
    Monteny E, Oleffe J, Donkerswolke M (1978) Methylmethacrylate hypersensitivity in a patient with cemented endoprosthesis. Acta Orthop Scand 49: 554–556PubMedGoogle Scholar
  26. 26.
    Fregert S (1983) Occupational hazards of acrylate bone cement in orthopedic surgery. Acta Orthop Scand 54: 787–789PubMedGoogle Scholar
  27. 27.
    Smith WDL (1977) Allergic contact dermatitis due to a triacrylate in ultraviolet cured inks. Contact Dermatitis 3: 312–314PubMedGoogle Scholar
  28. 28.
    Emmett EA, Kominsky JR (1977) Allergic contact dermatitis from ultraviolet cured inks. J Occup Med 19: 113–115PubMedGoogle Scholar
  29. 29.
    Emmett EA (1977) Contact dermatitis from polyfunctional acrylic monomers. Contact Dermatitis 3: 245–248PubMedGoogle Scholar
  30. 30.
    Nethercott JR (1978) Skin problems associated with multifunctional acrylic monomer in ultraviolet curing inks. Br J Dermatol 98: 541–552PubMedGoogle Scholar
  31. 31.
    Malten KE (1979) Recently reported causes of contact dermatitis due to synthetic resins and hardeners. Contact Dermatitis 5: 11–23PubMedGoogle Scholar
  32. 32.
    Björkner B, Dahlquist I (1979) Contact allergy caused by UV-cured acrylates. Contact Dermatitis 5: 403–404PubMedGoogle Scholar
  33. 33.
    Björkner B (1980) Allergic contact dermatitis from acrylates in ultraviolet curing inks. Contact Dermatitis 6: 405–409PubMedGoogle Scholar
  34. 34.
    Björkner B (1980) Allergenicity of trimethylol propane triacrylate in ultraviolet curing inks in the guinea pig. Acta Derm Venereol (Stockh) 60: 528–531Google Scholar
  35. 35.
    Malten KE (1982) Old and new, mainly occupational dermatological problems in the production and processing of plastics. In: Maibach HI, Gellin AG (eds) Occupational and industrial dermatology. Year Book, Chicago, pp 237–283Google Scholar
  36. 36.
    Björkner B (1984) The sensitizing capacity of multifunctional acrylates in the guinea pig. Contact Dermatitis 11: 236–246PubMedGoogle Scholar
  37. 37.
    Björkner B, Maibach HI (1987) Allergenicity of ultraviolet curable acrylic compounds and product development. Medical Device and Diagnostic Industry, April 1987Google Scholar
  38. 38.
    Taylor JS (1989) Acrylic reactions–ten-years’ experience. In: Frosch PJ, Dooms-Goossens A, Lachapelle J-M, Rycroft RJG, Scheper RJ (eds) Current topics in contact dermatitis. Springer, Berlin Heidelberg New York, pp 346–351Google Scholar
  39. 39.
    Fisher AA (1980) Cross reactions between methyl methacrylate monomer and acrylic monomers presently used in acrylic nail preparations. Contact Dermatitis 6: 345–347PubMedGoogle Scholar
  40. 40.
    Kanerva L, Estlander T, Jolanki R (1989) Occupational allergic contact dermatitis from acrylates: observations concerning anaerobic acrylic sealants and dental composite resins. In: Frosch PJ, Dooms-Goossens A, Lachapelle J-M, Rycrof RJG, Scheper RJ (eds) Current topics in contact dermatitis. Springer, Berlin Heidelberg New York, pp 352–359Google Scholar
  41. 41.
    Kanerva L, Estlander T, Jolanki R (1989) Allergic contact dermatitis from dental composite resins due to aromatic epoxy acrylates and aliphatic acrylates. Contact Dermatitis 20: 201–211PubMedGoogle Scholar
  42. 42.
    Fries IB, Fischer AA, Salvati EA (1975) Contact dermatitis in surgeons from methylmethacrylate bone cement. J Bone Joint Surg [Am] 57: 547–549PubMedGoogle Scholar
  43. 43.
    Jordan WP (1975) Cross-sensitization patterns in acrylate allergies. Contact Dermatitis 8: 13–15Google Scholar
  44. 44.
    Balda BR (1971) Allergic contact dermatitis due to acrylonitrile. Contact Dermatitis Newslett 9: 219Google Scholar
  45. 45.
    Balda BR (1975) Akrylonitril als Kontaktallergen. Hautarzt 26: 599PubMedGoogle Scholar
  46. 46.
    Romaquera C, Grimalt F, Vilaplana J (1985) Methyl methacrylate prosthesis dermatitis. Contact Dermatitis 12: 172Google Scholar
  47. 47.
    Malten KE (1987) Printing plate manufacturing process. In: Maibach HI (ed) Occupational and industrial dermatology, 2nd edn. Year Book, pp 351–366Google Scholar
  48. 48.
    Malten KE, van der Meer-Roosen CH, Seutter E (1978) Nyloprint-sensitive patients react to N,N’-methylene-bis-acrylamide. Contact Dermatitis 4: 214–222Google Scholar
  49. 49.
    Pedersen NB, Chevallier M-A, Senning A (1982) Secondary acrylamides in nyloprint printing plate as a source of contact dermatitis. Contact Dermatitis 8: 256–262PubMedGoogle Scholar
  50. 50.
    Edwards PM (1975) Neurotoxicity of acrylamide and its analogues and effects of these analogues and other agents on acrylamides neuropathy. Br J Ind Med 31–38Google Scholar
  51. 51.
    Calnan CD (1979) Cyanoacrylate dermatitis. Contact Dermatitis 5: 165–167PubMedGoogle Scholar
  52. 52.
    Malten KE (1982) Old and new, mainly occcupational dermatological problems in the production and processing of plastics. In: Maibach HI, Gellin GA (eds) Occupational and industrial dermatology. Year Book, pp 237–283Google Scholar
  53. 53.
    Pegum JC, Medhurst FA (1971) Contact dermatitis from penetration of rubber gloves by acrylic monomer. Br Med J 2: 141–143PubMedGoogle Scholar
  54. 54.
    Rietschel RL, Huggins R, Levy N, Pruitt PM (1984) In vivo and in vitro testing of gloves for protection against UV-curable acrylate resin systems. Contact Dermatitis 11: 279–282PubMedGoogle Scholar
  55. 55.
    Roed-Petersen J (1989) A new glove material protective against epoxy and acrylate monomer. In: Frosch PJ, Dooms-Goossens A, Lachapelle J-M, Rycroft RJG, Scheper RJ (eds) Current topics in contact dermatitis. Springer, Berlin Heidelberg New York, pp 603–606Google Scholar
  56. 56.
    Kanerva L, Estlander T, Jolanki R (1988) Sensitization to patch test acrylates. Contact Dermatitis 18: 10–15PubMedGoogle Scholar
  57. 57.
    Thorgeirsson A, Fregert S (1977) Allergenicity of epoxy resins in the guinea pig. Acta Derm Venereol (Stockh) 57: 253–356Google Scholar
  58. 58.
    Fregert S (1981) Manual of contact dermatitis, 2nd edn. Munksgaard, CopenhagenGoogle Scholar
  59. 59.
    Fregert S (1987) Contact dermatitis from epoxy resin systems. In: Maibach HI (ed) Occupational and industrial dermatology, 2nd edn. Year Book, Chicago, pp 341–345Google Scholar
  60. 60.
    Burrows D, Fregert S, Campbell H, Trulsson L (1984) Contact dermatitis from the epoxy resins tetraglycidyl-4,4’-methylene dianiline and o-diglycidyl phthalate in composite material. Contact Dermatitis 11: 80–82PubMedGoogle Scholar
  61. 61.
    Thorgeirsson A, Fregert S, Magnusson B (1975) Allergenicity of epoxy-reactive diluents in the guinea pig. Berufsdermatosen 23: 178–183PubMedGoogle Scholar
  62. 62.
    Jolanki R, Estlander T, Kanerva L (1987) Occupational contact dermatitis and contact urticaria caused by epoxy resins. Acta Derm Venereol Suppl (Stockh) 134: 90–94Google Scholar
  63. 63.
    Dahlquist I, Fregert S (1979) Allergic contact dermatitis from volatile epoxy hardeners and reactive diluents. Contact Dermatitis 5: 406–407PubMedGoogle Scholar
  64. 64.
    Fregert S, Thorgeirsson A (1977) Patch testing with low molecular oligomers of epoxy resins in humans. Contact Dermatitis 3: 301–303PubMedGoogle Scholar
  65. 65.
    Fregert S (1988) Physiochemical methods for detection of contact allergens. In: Taylor JS (ed) Occupational dermatoses. Saunders, Philadelphia, pp 97–104 (Dermatological clinics, vol 6 )Google Scholar
  66. 66.
    Fregert S, Trulsson L (1978) Simple methods for demonstration of epoxy resin of bisphenol A type. Contact Dermatitis 4: 69PubMedGoogle Scholar
  67. 67.
    Jolanki R, Sysilampi M-L, Kanerva L, Estlander T (1989) Contact allergy to cycloaliphatic epoxy resins. In: Frosch PJ, Dooms-Goossens A, Lachapelle J-M, Rycroft RJG, Scheper RJ (eds) Current topics in contact dermatitis. Springer, Berlin Heidelberg New York, pp 360–367Google Scholar
  68. 68.
    Lembo G, Balato N, Cusano F, Baldo A, Ayala F (1989) Contact dermatitis to epoxy resins in composite material. In: Frosch PJ, Dooms-Goossens A, Lachapelle J-M, Rycroft RJG, Scheper RJ (eds) Current topics in contact dermatitis. Springer, Berlin Heidelberg New York, pp 377–380Google Scholar
  69. 69.
    Thorgeirsson A (1978) Sensitization capacity of epoxy resin hardeners in the guinea pig. Acta Derm Venereol (Stockh) 58: 332–336Google Scholar
  70. 70.
    Mathias CGT (1987) Allergic contact dermatitis from a nonbisphenol A epoxy in a graphite fiber reinforced epoxy laminate. J Occup Med 29: 754–755PubMedGoogle Scholar
  71. 71.
    Lachapelle JM, Tennstedt D, Dumont-Fruytier M (1978) Occupational allergic contact dermatitis to isophorone diamine ( IPD) used as an epoxy resin hardener. Contact Dermatitis 4: 109–112Google Scholar
  72. 72.
    Dahlquist I, Fregert S (1979) Contact allergy to the epoxy hardener isophoronediamine ( IPD ). Contact Dermatitis 5: 120–121Google Scholar
  73. 73.
    Thorgeirsson A (1978) Sensitization capacity of epoxy reactive diluents in the guinea pig. Acta Derm Venereol (Stockh) 58: 329–331Google Scholar
  74. 74.
    Dahlquist I, Fregert S (1979) Contact allergy to Cardura RE, an epoxy reactive diluent of the ester type. Contact Dermatitis 5: 121–122PubMedGoogle Scholar
  75. 75.
    Rudzki E, Krajewska D (1979) Contact sensitivity to phenolglycidyl ether. Derm Beruf Umwelt 27: 42–44PubMedGoogle Scholar
  76. 76.
    Lovell CR, Rycroft RJG, Mahood J (1984) Isolated cardura E10 sensitivity in an epoxy resin chemical process. Contact Dermatitis 11: 190–191PubMedGoogle Scholar
  77. 77.
    Prens EP, de Jong G, van Joost T (1986) Sensitization to epichlorohydrin and epoxy system components. Contact Dermatitis 15: 85–90PubMedGoogle Scholar
  78. 78.
    Van Joost T (1988) Occupational sensitization to epichlorohydrin and epoxy resin. Contact Dermatitis 19: 278–280PubMedGoogle Scholar
  79. 79.
    Pegum JS (1979) Penetration of protective gloves by epoxy resin. Contact Dermatitis 5: 281–283PubMedGoogle Scholar
  80. 80.
    Blanken R, Nater JP, Veenhoff E (1987) Protection against epoxy resins with glove materials. Contact Dermatitis 16: 46–47PubMedGoogle Scholar
  81. 81.
    Blanken R, Nater JP, Veenhoff E (1987) Protective effect of barrier creams and spray coatings against epoxy resins. Contact Dermatitis 16: 79–83PubMedGoogle Scholar
  82. 82.
    Estlander T, Jolanki R (1988) How to protect the hands. In: Taylor JS (ed) Occupational dermatoses. Saunders, Philadelphia, pp 105–114 (Dermatological clinics, vol 6 )Google Scholar
  83. 83.
    Bruze M (1985) Contact sensitizers in resins based on phenol and formaldehyde. Acta Derm Venereol Suppl (Stockh) 119: 1–83Google Scholar
  84. 84.
    Stevenson CJ (1981) Occupational vitiligo: clinical and epidemiological aspects. Br J Dermatol 105: [Suppl] 51–56PubMedGoogle Scholar
  85. 85.
    Bruze M, Almgren G (1988) Occupational dermatoses in workers exposed to resins based on phenol and formaldeyhde. Contact Dermatitis 19: 272–277PubMedGoogle Scholar
  86. 86.
    Foussereau J, Cavelier C, Selig D (1976) Occupational eczema from para-tertiarybutylphenol formaldehyde resins: a review of the sensitizing resins. Contact Dermatitis 2: 254–258PubMedGoogle Scholar
  87. 87.
    Schubert H, Agatha G (1979) Zur Allergennatur der para-tert. Butylphenolformaldehydeharze. Derm Beruf Umwelt 27: 49–52Google Scholar
  88. 88.
    Högberg M, Wahlberg JE (1980) Health screening for occupational dermatoses in house painters. Contact Dermatitis 6: 100–106PubMedGoogle Scholar
  89. 89.
    Fregert S (1981) Contact allergy to phenoplastics. Contact Dermatitis 7: 170PubMedGoogle Scholar
  90. 90.
    Bruze M (1988) Patch testing with a mixture of 2 phenol-formaldehyde resins. Contact Dermatitis 19: 116–119PubMedGoogle Scholar
  91. 91.
    Bruze M (1986) Simultaneous reactions to phenol-formaldehyde resins colophony/hydroabietyl alcohol and balsam of Peru/perfume mixture. Contact Dermatitis 14: 119–120PubMedGoogle Scholar
  92. 92.
    Bruze M, Zimerson E (1985) Contact allergy to 3-methylol phenol, 2,4-dimethylol phenol and 2,6-dimethylol phenol. Acta Derm Venereol (Stockh) 65: 548–551Google Scholar
  93. 93.
    Bruze M (1986) Sensitizing capacity of 4,4’-dihydroxy-(hydroxymethyl)-diphenyl methanes in the guinea pig. Acta Derm Venereol (Stockh) 66: 110–116Google Scholar
  94. 94.
    Lubach D (1978) Erkrankung durch Diisocyanate, pt 1: Schaden der Atemwege and der Haut. Derm Beruf Umwelt 26: 184–187PubMedGoogle Scholar
  95. 95.
    White IR, Stewart JR, Rycroft AJ (1983) Allergic contact dermatitis from an organic di-isocyanate. Contact Dermatitis 9: 300–303PubMedGoogle Scholar
  96. 96.
    Malten KE (1984) Dermatological problems with synthetic resins and plastics in glues, part I. Derm Beruf Umwelt 32: 81–86PubMedGoogle Scholar
  97. 97.
    Malten KE (1984) Dermatological problems with synthetic resins and plastics in glues, part II. Derm Beruf Umwelt 32: 118–125PubMedGoogle Scholar
  98. 98.
    Tanaka K, Takeoka A, Nishimura F, Hanada S (1987) Contact sensitivity induced in mice by methylene bisphenyl diisocyanate. Contact Dermatitis 17: 199–204PubMedGoogle Scholar
  99. 99.
    Cronin E (1980) Contact dermatitis. Churchill Livingstone, Edinburgh, pp. 575–663Google Scholar
  100. 100.
    Adams RM (1990) Occupational skin disease, 2nd ed n. Saunders, Philadelphia, pp. 387–394Google Scholar
  101. 101.
    Fisher AA (1986) Contact dermatitis, 3rd edn. Lea and Febiger, Philadelphia, pp 546–565Google Scholar
  102. 102.
    Vale PT, Rycroft RJG (1988) Occupational irritant contact dermatitis from fibreboard containing urea-formaldehyde resin. Contact Dermatitis 19: 62PubMedGoogle Scholar
  103. 103.
    Mathias CGT (1988) Allergic contact dermatitis from triglycidyl isocyanurate in polyester paint pigments. Contact Dermatitis 19: 67–68PubMedGoogle Scholar
  104. 104.
    Mac Farlane AW, Curley RK, King CM (1986) Contact sensitivity to unsaturated polyester resins in a limb prosthesis. Contact Dermatitis 15: 301–303Google Scholar
  105. 105.
    Lidén C, Löfström A, Storgards-Hatam K (1984) Contact allergy to unsaturated polyester in a boatbilder. Contact Dermatitis 11: 262–263PubMedGoogle Scholar
  106. 106.
    Malten KE, Zielhuis RL (1964) Industrial toxicology and dermatology in the production and processing of plastics. Elsevier, New YorkGoogle Scholar
  107. 107.
    Vidovic R, Kansky A (1985) Contact dermatitis in workers processing polyvinyl chloride plastics. Derm Beruf Umwelt 33: 104–105PubMedGoogle Scholar
  108. 108.
    Schulsinger C, Möllegaard K (1980) Polyvinyl chloride dermatitis not caused by phthalates. Contact Dermatitis 6: 477–480PubMedGoogle Scholar
  109. 109.
    Fregert S, Meding B, Trulsson L (1984) Demonstration of epoxy resin in stoma pouch plastic. Contact Dermatitis 10: 106PubMedGoogle Scholar
  110. 110.
    Fregert S, Trulsson L, Zimerson E (1982) Contact allergic reaction to diphenylthiourea and phenylisothiocyanate in PVC adhesvie tape. Contact Dermatitis 8: 38–42PubMedGoogle Scholar
  111. 111.
    Sjöborg S, Fregert S, Trulsson L (1984) Contact allergy to styrene and related chemicals. Contact Dermatitis 10: 94–96PubMedGoogle Scholar
  112. 112.
    Bruze M, Boman A, Bergqvist-Karlsson A, Björkner B, Wahlberg JE, Voog E (1988) Contact allergy to cyclohexanone resin in humans and guinea pigs. Contact Dermatitis 18: 46–49PubMedGoogle Scholar
  113. 113.
    Heine A, Laubstein B (1990) Contact dermatitis from cyclohexanone-formaldehyde resin (L2 resin) in a hair lacquer spray. Contact Dermatitis 22: 108PubMedGoogle Scholar
  114. 114.
    Niklasson B, Björkner B (1989) Contact allergy to the UV-absorber Tinuvin P in plastics. Contact Dermatitis 21: 330–334PubMedGoogle Scholar
  115. 115.
    Jolanki R, Kanerva L, Estlander T (1987) Organic pigments in plastics can cause allergic contact dermatitis. Acta Derm Venereol Suppl (Stockh) 134: 95–97Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1992

Authors and Affiliations

  • Bert Björkner

There are no affiliations available

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