Template:Ref-Streeter1951
From Embryology
Streeter GL. Developmental horizons in human embryos. Description of age groups XIX, XX, XXI, XXII, and XXIII, being the fifth issue of a survey of the Carnegie Collection (prepared for publication by C. H. Heuser and G. W. Corner). (1951) Carnegie Instn. Wash. Publ. 592, Contrib. Embryol., 34: 165-196.
