"There is a large literature relating to twins in their purely surgical and physiological aspect. The reader interested in this should consult Die Lehre von den Zwillingen, von L. Kleinwächter, Prag. 1871. It is full of references, but it is also unhappily disfigured by a number of numerical misprints, especially in page 26. I have not found any book that treats of twins from my present point of view."

Barbaro, N., Richardson, G. B., Nedelec, J. L., & Liu, H. (2020). Assessing Effects of Life History Antecedents on Age at Menarche and Sexual Debut Using a Genetically Informative Design [Preprint]. PsyArXiv. https://doi.org/10.31234/osf.io/xqfg8