Vanest, Jean-Marie, et al. “Helicenes: The Photochemical Ring-Closure of Polymer-Supported 1,2-Diarylethylenes: Hexahelicene- and benzo[c]phenanthrene-2-Carbaldehyde”. CHIMIA, vol. 29, no. 8, Aug. 1975, p. 343, https://doi.org/10.2533/chimia.1975.343.