Kuz'mina, L.G., Perepichka, I.F., Perepichka, D.F., Howard, J.A., Bryce, M.R., "Supramolecular architecture of two charge-transfer complexes based on 2,7-(X,X)-4,5-dinitro-9-dicyanomethylenefluorenes (X=NO2 or CN) and tetrathiafulvalene", Crystallography Reports, 2002