1. König's theorem;Grzegorz Bancerek;Formalized Mathematics,1990
2. Cartesian product of functions;Grzegorz Bancerek;Formalized Mathematics,1991
3. Joining of decorated trees;Grzegorz Bancerek;Formalized Mathematics,1993
4. Subtrees;Grzegorz Bancerek;Formalized Mathematics,1996
5. Institution of many sorted algebras. Part I: Signature reduct of an algebra;Grzegorz Bancerek;Formalized Mathematics,1997