Saifurrahman, M., P. Sudira, and R. W. Daryono. “The Determinant Factor of the Principal Leadership Solutions in Facing the 21st-Century Learning”. Jurnal Pendidikan Dan Pengajaran, vol. 54, no. 2, July 2021, pp. 230-43, doi:10.23887/jpp.v54i2.34102.