Prepn: FR 1594628; K. Ley et al., US 3908008 (1970, 1975 to Bayer). Growth promotant activity for pigs: R. S. Barber et al., Anim. Feed Sci. Technol. 4, 117 (1979). HPLC analysis: G. F. Bories, J. Chromatogr. 172, 505 (1979). LC determn in animal feeds: F. J. dos Ramos et al., ibid. 558, 125 (1991).