1. Davey, B.A., Pristley, H.A.: Introduction to Lattices and Order. Cambridge (1994)
2. Ershov, Y.L., Lavrov, I.A., Taimanov, A.D., Taitslin, M.A.: Elementary theories. Uspechi Mat. Nauk 20(4), 37–108 (1965) (in Russian)
3. Ershov, Y.L.: Undecidability of some fields. DAN SSSR (Reports of AS USSR) 161(1), 27–29 (1965)
4. Hertling, P.: Unstetigkeitsgrade von Funktionen in der effectiven Analysis. Ph.D thesis, FernUniversität Hagen, Informatik-Berichte 208–11 (1996)
5. Lecture Notes in Computer Science;S. Kosub,2000