1. Azetidines, Azetines and Azetes: Monocyclic;Andresini,2022
2. Oxetanes and Oxetenes: Monocyclic;Rojas,2022
3. Thietanes and Thietes: Monocyclic;Didier,2022
4. Four-Membered Rings With Two Nitrogen Atoms;Lecornué,2022
5. Four-Membered Rings With One Oxygen and One Nitrogen Atom;Orentas,2022