Kata Kunci Pencarian:
- Daftar masalah matematika yang belum terpecahkan
- Ruang Banach
- Köthe conjecture
- List of conjectures
- List of unsolved problems in mathematics
- Nil ideal
- Gottfried Köthe
- Jacobson radical
- Radical of a ring
- Levitzky's theorem
- Deaths in April 1989
- Nilpotent ideal
