"Degree of Resemblance of Parents and Offspring with Respect to Birth as Twins for Registered Shropshire Sheep" by Rietz, H.L. and Roberts, E, 1915

"Degree of Resemblance of Parents and Offspring with Respect to Birth as Twins for Registered Shropshire Sheep" by Rietz, H.L. and Roberts, E, 1915, Box: 4, Folder: 27. Personal papers of John "Jack" A. Weir, PP 404. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/261363 Accessed December 25, 2025.