5[7]El-kassaby Y A,Fashler A M K,Sziklai O. Reproductive phenology and its impact on gentically improved seed production in a Douglas-fir seed orchard [J] .Silvae Genet, 1984,33(4~5).
6[8]Askew G R,et al. An index of phenololgical overlap in flowering for clonal seed orchards. Silvea Genet, 1990.39(3~4).