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Beck GJ, van den Berg BJ.Beck GJ, et al. Among authors: van den berg bj.J Pediatr. 1975 Apr;86(4):504-11. doi: 10.1016/s0022-3476(75)80138-7.J Pediatr. 1975.PMID: 1127496
Christianson RE, van den Berg BJ, Milkovich L, Oechsli FW.Christianson RE, et al. Among authors: van den berg bj.Am J Public Health. 1981 Dec;71(12):1333-41. doi: 10.2105/ajph.71.12.1333.Am J Public Health. 1981.PMID: 7315998Free PMC article.