Sorokowski, Piotr, Marta Kowal, Piotr Badyna, Agnieszka Niemczyk, Maciej Karwowski, and Sławomir Kozieł. 2019. “Testing the Trivers-Willard Hypothesis on Polish Kings and Dukes”. Anthropological Review 82 (4):397-404. https://doi.org/10.2478/anre-2019-0030.