1. The ordinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
2. The complex numbers;Czesław Byliński;Formalized Mathematics,1990
3. Solving roots of polynomial equation of degree 2 and 3 with complex coefficients;Yuzhong Ding;Formalized Mathematics,2004
4. Basic properties of real numbers;Krzysztof Hryniewiecki;Formalized Mathematics,1990