title: Vitamin A, limb patterns and the search for the positional code.
mesh_terms: D000663:Amphibians; D000818:Animals; D001717:Birds; D005121:Extremities / Q000502:physiology; D009024:Morphogenesis / Q000187:drug effects*; D012038:Regeneration / Q000187:drug effects*; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D014801:Vitamin A