8Prum R O.Williamson S.Theory of the growth and evolution of feather shape[J].Journal of Experimental Zoology,2001,291(1):30-57.
9Xu R F.Wu W.Xu H.Investigation of feather follicle development in Embryonic geese[J].Poultry Science,2007,86(9):2000-2007.
10Alibardi L,Toin M.Cytochemical and molecular characteristics of the process of comification during feather morphogenesis[J].Progress in Histochemistry and Cytochemistry,2008,43(1):1-69.