Bovy, P., Lenaers, A., Callaert, M., Herickx, N., Gillet, C., Roba, J., Dethy, JM., Callaertdeveen, B., & Janssens, M. (1988). Synthesis and Aldose Reductase Inhibition-activity of Spiro-[9h-fluoren-9,4′-imidazolidine]-2′,5′-dione Derivatives. European Journal of Medicinal Chemistry, 23(2), 165-172. https://doi.org/10.1016/0223-5234(88)90190-0 (Original work published 1988)