Taylor, R.N., and Williams, L.T. 1988. Developmental expression of platelet-derived growth factor and its re- 
ceptor in the human placenta. Mol Endocrinol 2:627-632. 
Williams, L.T. 1989- Signal transduction by the platelet-derived growth factor receptor. Science 243:1564- 
1570. 
Williams, L.T, Escobedo, J.A., Keating, M.T, and Coughlin, S.R. 1988. Signal transduction by the platelet-de- 
rived growth factor receptor. Cold Spring Harb Symp Quant Biol 53:455-465. 
129 
