Edi Sumarno, Ginting, J. S., Karina, N., & Lubis, M. A. R. (2019). The Factors in the Emergence of Smallholder Rubber Plantation in Tapanuli: 1906 - 1942. International Journal of Culture and Art Studies, 3(1), 22-29. https://doi.org/10.32734/ijcas.v3i1.2623