Fernandez-Manjarres, J., Gerard, P., Dufour, J., Raquin, C. & Frascaria-lacoste, N. 2006. Differential patterns of morphological and molecular hybridization between Fraxinus excelsior L. and Fraxinus angustifolia Vahl (Oleaceae) in eastern and western France. <em>Molecular Ecology</em>, 15(11): 3245-3257.