1. Cardinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
2. The fundamental properties of natural numbers;Grzegorz Bancerek;Formalized Mathematics,1990
3. König's theorem;Grzegorz Bancerek;Formalized Mathematics,1990
4. The ordinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
5. Monoids;Grzegorz Bancerek;Formalized Mathematics,1992