Na Takuathung, Chakrit, and Piyawat Diloksumpun. 2020. “An Assessment of Physical Workload of Timber Harvesting Workers in Teak Plantation, Phrae Province”. Thai Journal of Forestry 39 (1). Bangkok, Thailand:125-34. https://li01.tci-thaijo.org/index.php/tjf/article/view/246001.