 Initially, Chinese was used for writing purposes, but by the 13th century, a set of derivative characters known as Chữ Nôm emerged that allowed native Vietnamese words to be written.However, it remained limited to poetry, literature, and practical texts like medicine while all state and official documents were written in Classical Chinese.Aside from some mining and fishing, agriculture was the primary activity of most Vietnamese, and economic development and trade were not promoted or encouraged by the state.