- Marine research in Indonesia: Issues 16-20 - Page 229 Lembaga Oceanology Nasional (Indonesia), Lembaga Ilmu Pengetahuan Indonesia - 1976 "The Ca River is the longest river in the central part of Vietnam, the main length belongs to Nghệ An and Hà Tĩnh provinces. This river possesses abundant natural resources and habitats of many valuable plants and animals,"
- Journal of Geology: Issues 9-12 Cục địa chất Việt Nam - 1997 "2. 7. Cả River zone: This zone lies along the Cả River and Rào Nay basins, with a length of 300 km"