... at the end of the eighth century when the title of Bố Cái Ðại Vương (Father and mother of the people) was given by his successor and his subjects to Phùng Hưng , who, in 791,overthrew the then ... the Trịnh in the North and the Nguyễn in the South, both claiming to be followers of the Lê . It ended only in 1672 with the agreement to use the River of Linh (Linh giang ) as the demarcation ... Thịnh of the Tây Sơn and his brothers. The social and political background of this long period covering the seventeenth and the eighteenth centuries had a great impact on the development of the Vietnameseliterature...