Romeida, Atra, et al. “Embryogenic Callus Induction of Pencil Orchid (Papilionanthe Hookeriana Rchb.F.) Through in Vitro Culture”. International Journal on Advanced Science, Engineering and Information Technology, vol. 6, no. 2, Mar. 2016, pp. 196-00, doi:10.18517/ijaseit.6.2.703.