Professor Wang Li’s essay "Han Yue Yu Yanjiu" (“A Study of Sino-Vietnamese”), published in The Lingnan Journal in 1948, is regarded as a landmark contribution in the field of Sino–Vietnamese linguistics. In this work, he divides the Vietnamese lexicon into two major strata: native Vietnamese words and Sino-Vietnamese words. Furthermore, he distinguishes three layers within the phonological system of Sino-Vietnamese vocabulary: Sino-Vietnamese, Old Sino-Vietnamese, and Vieticized Chinese. Wang Li’s pioneering exploration of these historical strata, proposed more than half a century ago, continues to offer valuable insights and remains highly influential today.