1. Cardinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
2. The ordinal numbers;Grzegorz Bancerek;Formalized Mathematics,1990
3. Countable sets and Hessenberg's theorem;Grzegorz Bancerek;Formalized Mathematics,1991
4. Joining of decorated trees;Grzegorz Bancerek;Formalized Mathematics,1993
5. Mizar analysis of algorithms: Preliminaries;Grzegorz Bancerek;Formalized Mathematics,2007