Wojtusik, J., Brandicourt, I., Rice, W. and 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), pp. 181-187. doi: 10.19227/jzar.v8i3.494.