1. Cardinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
2. Segments of natural numbers and finite sequences;Grzegorz Bancerek;Formalized Mathematics,1990
3. Group and field definitions;Józef Białas.;Formalized Mathematics,1990
4. Binary operations;Czesław Byliński;Formalized Mathematics,1990
5. Functions and their basic properties;Czesław Byliński;Formalized Mathematics,1990