1. Wells HG, The outline of history, Newnes, 1920.
2. Asking questions;Sudman,1982
3. Designing surveys;Blair,1996
4. American Association for Public Opinion Research Code of Professional Ethics and Practices (I.A.3.).
5. http://www.oosa.unvienna.org/Third United Nation Conference on the Exploration and Peaceful Uses of Outer Space (1998). Education and Training in Space Science and Technology.Third United Nation Conference on the Exploration and Peaceful Uses of Outer Space (1998). Basic Space Science and Microgravity Research and their Benefits.