Heterocyclic compounds include all nucleic acids, many sugars, vitamins, hormones, antibiotics and other synthetic pharmaceuticals, most dyes, pesticides and weedkillers. The eight volumes of this major work of reference are the most authoritative, modern and complete ever published on the subject. They give an up-to-date overview of the whole area appropriate to the needs of researchers, teachers and others with an interest in the subject and its applications, provide detailed information to answer specific questions, demonstrate exactly what is known or not known on a given topic, and direct attention to more detailed reviews. A systematic arrangement of the chapters provides a uniform treatment throughout and allows very easy access to the primary literature. Volume 6 specifically deals with the structure, reactivity, synthesis and applications of five-membered ring compounds containing two or more oxygen, sulfur or nitrogen atoms.