Hayati, R.N. et al. 2021. Estrous Signs and Progesterone Profile of Ongole Grade Cows Synchronized at Different Ages Fed Different Level of Dietary Crude Protein. Tropical Animal Science Journal. 44, 1 (Mar. 2021), 16–23. DOI:https://doi.org/10.5398/tasj.2021.44.1.16.