Development of Integrated STEM-PjBL e-LKPD on Acid-Base Materials for Class XI SMA using Flip PDF Proffesional Software. EPK [Internet]. 2023 June 23 [cited 2026 Oct. 28];4(2):31-9. Available from: http://entalpipendidikan.ppj.unp.ac.id/index.php/epk/article/view/314