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Doolittle DJ, Rahn CA, Burger GT, Davis R, deBethizy JD, Howard G, Lee CK, McKarns SC, Riccio E, Robinson J, et al.Doolittle DJ, et al.Mutat Res. 1989 Jun;223(2):221-32. doi: 10.1016/0165-1218(89)90050-5.Mutat Res. 1989.PMID: 2739680Clinical Trial.