Kumar, V.V.A., et al. “Facile Synthesis of 8-Hydroxymethyl-8,9-Dihydro-2H-furo[2,3-h]chromene-3-Carbaldehyde”. Asian Journal of Chemistry, vol. 25, no. 12, June 2013, pp. 6738-40, doi:10.14233/ajchem.2013.14523.