ติ๊กจ๊ะ ว., หน่อใหม่ ฐ., จิตต์บุรุษ อ., and ภูมิลา อ. “PERIODIC WITH PERIOD 4 OF A PIECEWISE LINEAR SYSTEM OF DIFFERENCE EQUATIONS WITH INITIAL CONDITIONS BEING SOME POINTS ON POSITIVE Y AXIS”. PSRU Journal of Science and Technology, vol. 3, no. 2, Aug. 2018, pp. 26-34, https://ph01.tci-thaijo.org/index.php/Scipsru/article/view/125217.