Wojtusik, J., Brandicourt, I., Rice, W., & Roth, T. (2020). Reproductive cycle and pregnancy monitoring in the common hippopotamus (Hippopotamus amphibius) through salivary steroid analyses and trans-abdominal ultrasonography . Journal of Zoo and Aquarium Research, 8(3), 181-187. https://doi.org/10.19227/jzar.v8i3.494