Figure 5E. Reprinted with permission from Elsevier from [doi:10.1016/j.ydbio.2006.02.002] Dev Biol 2006 May 15;293(2):370-81, Andersson O; Reissmann E; Jornvall H; Ibanez CF, "Synergistic interaction between Gdf1 and Nodal during anterior axis development." Copyright 1995 [PMID:7556909] .