Ghasem, N. M., and M. A. Hussain. “Avoiding Chaotin Instability under PID Control of Plythylene Fluidized Bed Reactor (UNIPOL Procees)”. ASEAN Journal of Chemical Engineering, Vol. 3, no. 1, Dec. 2003, pp. 26-33, https://journal.ugm.ac.id/v3/AJChE/article/view/7575.