- Trading of textbooks, books, school equipmentd and stationeries.

- Joint venture with companies in Nam Dinh Province to issue books, magazines, map, picture, CDs, and other education products.

- Others under business license.

- DST originated from Textbook Department, established in 1983, belonging to Department of Nam Dinh Education & Training;

- October 1992: DST changed into Nam Ha School Books & Equipment Company;

- 1996: DST was renamed as Nam Dinh School Books & Equipment Company;

- 29 December 2004: DST changed as Nam Dinh School Books & Equipment JSC., with a charter capital of VND3 billion;

- 16 October 2007: Listed on HNX;

- 28 February 2016: Charter capital was raised up to VND323 billion; 

- 08 January 2018: Renamed as Sao Thang Long Investment Joint Stock Company.