Planting technique and maintenance of immature rubber treers in peam cheang plantation បច្ចេកទេសដាំដុះ និងថែទាំកូនកៅស៊ូនៅចំការកៅស៊ូពាមជាំង KHEN, SOKCHEAT. AGR KHE 1999 B024 Or.1 Phnom Penh RUA 1999 1999 Text 52p. https://drive.google.com/file/d/16TJgYhqSLMobw7bCbYt7LgXoT_AXqVGn/view?usp=sharing