1. Cardinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
2. The fundamental properties of natural numbers;Grzegorz Bancerek;Formalized Mathematics,1990
3. Increasing and continuous ordinal sequences;Grzegorz Bancerek;Formalized Mathematics,1990
4. The ordinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
5. Functions and their basic properties;Czesław Byliński;Formalized Mathematics,1990