A. Romeida, D. W. Ganefianti, and .-. Rustikawati, “Embryogenic Callus Induction of Pencil Orchid (Papilionanthe hookeriana Rchb.f.) Through in Vitro Culture”, Int. J. Adv. Sci. Eng. Inf. Technol., vol. 6, no. 2, pp. 196–200, Mar. 2016.