SEARCH Articles Figures Tables HETEROATOMS AND HETEROCYCLIC COMPOUNDS Heteroatom compounds Heteroatom heterocycles Heteroatomic compounds Heteroatoms Heterocycles Heterocycles Heteroatoms in Cyclic Organic Compounds Heterocyclic compounds Cyclic organic heteroatoms, atoms other than Heterocyclic compounds four heteroatomic rings Heterocyclic compounds three heteroatomic rings