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Hartman BK, Agrawal HC, Agrawal D, Kalmbach S.Hartman BK, et al. Among authors: agrawal hc, agrawal d.Proc Natl Acad Sci U S A. 1982 Jul;79(13):4217-20. doi: 10.1073/pnas.79.13.4217.Proc Natl Acad Sci U S A. 1982.PMID: 6180437Free PMC article.