Prepn by nitration of fluorenone: Schmidt, Bauer, Ber. 38, 3758 (1905); Orchin et al., J. Am. Chem. Soc. 69, 1225 (1947); by nitration of 2,5-dinitrofluorenone: Ray, Francis, J. Org. Chem. 8, 58 (1943). Structure: Bell, J. Chem. Soc. 1928, 1990. Crystal structure: D. L. Dorset et al., Acta Crystallogr. B28, 3122 (1972); H. L. Ammon, ibid. B29, 2314 (1973). Carcinogenicity study: C. Huggins, N. C. Yang, Science 137, 257 (1962). Evaluation of employee exposure to TNF in workplace using HPLC: M. J. Seymour, J. Chromatogr. 236, 530 (1982); R. E. McCullen, A. N. Sanghvi, ASTM Spec. Tech. Publ. 786, 26 (1982).