Nurwahyuni, Endah, and Eka Tarwaca Susila Putra. 2020. “Calcium Addition Improving Pectin Level in Oil Palm Seedlings (Elaeis Guineensis Jacq.)”. Jurnal Penelitian Kelapa Sawit 28 (3), 169-78. https://doi.org/10.22302/iopri.jur.jpks.v28i3.111.