M. Salazar-Carranza, G. Castillo-Badilla, J. Murillo-Herrera, F. Hueckmann-Voss, and J. J. Romero-Zuñiga, “Age at first calving in Holstein dairy cows specialized in Costa Rica”., Agron. Mesoam., vol. 24, no. 2, pp. 233–243, Nov. 2013.