The Paracel and Strattle islands belong to the sovereignty of Vietnam through publications on geographical and historical discoveries in the kingdom of Spain in the period of 1841-1847

During the reign of King Thieu Tri in Dai Nam, Vietnam, the "First Opium War" in China from 1840-1842 was not only the focus of attention of the Far Eastern countries, but also the focus of attention from the European and American public opinion. Many scholars and publishers in the continents of Europe, Asia, and America continuously published scientific publications on geography, navigation, commerce, history, etc. to promptly meet the need for knowledge of the era about China and related countries in this vast region of Asia. In that context, the Kingdom of Spain, a Western colonial power that had a foothold in the Philippines since the 16th century, also published many works about Asian countries, including publications that mentioned the “Parace-los”/Hoang Sa-Truong Sa archipelago located in the geographical territory of Cochinchina, Dang Trong under the sovereignty of the Annam Empire (now Vietnam) since 1816.