P. Poolchak, W. Kaewwiset, P. Naemchanthara, E. Hoonnivathana, P. Limsuwan, and K. Naemchanthara, “Effect of Manganese Addition on Structure and Properties of Hydroxyapatite Synthesized from Eggshells”, RMUTSB Acad. J., vol. 3, no. 2, pp. 182–190, Jul. 2015.