Expression of VEGFR‐2 and AC133 by circulating human CD34+ cells identifies a population of functional endothelial precursors. - Peichev,M.; Naiyer,A.J.; Pereira,D.; Zhu,Z.; Lane,W.J.; Williams,M.; Oz,M.C.; Hicklin,D.J.; Witte,L.; Moore,M.AS.; Rafii,S. (Blood, 2000)