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Ekstrand A, Groop L, Pettersson E, Grönhagen-Riska C, Laatikainen L, Matikainen E, Seppäläinen AM, Laasonen E, Summanen P, Ollus A, et al.Ekstrand A, et al. Among authors: summanen p.J Intern Med. 1992 Sep;232(3):253-61. doi: 10.1111/j.1365-2796.1992.tb00580.x.J Intern Med. 1992.PMID: 1402622