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Zwolinski, J. B.; Swart, W. J.; Wingfield, M. J. (1990-12-01). "Economic impact of a post-hail outbreak of dieback induced by Sphaeropsis sapinea". European Journal of Forest Pathology. 20 (6–7): 405–411. doi:10.1111/j.1439-0329.1990.tb01155.x. ISSN1439-0329. S2CID85072546.
Zwolinski, J. B.; Swart, W. J.; Wingfield, M. J. (1990-12-01). "Economic impact of a post-hail outbreak of dieback induced by Sphaeropsis sapinea". European Journal of Forest Pathology. 20 (6–7): 405–411. doi:10.1111/j.1439-0329.1990.tb01155.x. ISSN1439-0329. S2CID85072546.