Kaewlamun, W.; Chayaratanasin, R.; Virakul, P.; Ponter, A. A.; Humblot, P.; Suadsong, S.; Tummaruk, P.; Techakumphu, M. Differences of Periods of Calving on Days Open of Dairy Cows in Different Regions and Months of Thailand. TJVM 2013, 41, 315-320.