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Tashkin DP, Rand C, Nides M, Simmons M, Wise R, Coulson AH, Li V, Gong H Jr.Tashkin DP, et al.Am J Med. 1991 Oct 21;91(4A):33S-36S. doi: 10.1016/0002-9343(91)90260-5.Am J Med. 1991.PMID: 1951401Clinical Trial.