The series "Studies in Fuzziness and Soft Computing" publishes monographs and edited volumes on various topics in soft computing, including fuzzy sets, rough sets, neural networks, evolutionary computation, probabilistic and evidential reasoning, multi-valued logic, and related fields. The series is known for its rapid publication and global distribution, allowing quick dissemination of research results. The books are indexed by ISI, DBLP, Ulrichs, SCOPUS, Zentralblatt Math, GeoRef, Current Mathematical Publications, IngentaConnect, MetaPress, and SpringerLink. They are also submitted for indexing to Web of Science. The book "Interval-Valued Intuitionistic Fuzzy Sets" by Krassimir T. Atanassov explores the theory and applications of interval-valued intuitionistic fuzzy sets (IVIFSs), an extension of intuitionistic fuzzy sets (IFSs) introduced by Atanassov in 1983. IVIFSs were further developed by Georgi Gargov in 1989. The book presents Atanassov's main results and their applications, focusing on the most interesting ones. It covers various aspects of IVIFSs, including definitions, operations, relations, and operators. The book also discusses applications in areas such as fuzzy graphs, neural networks, generalized nets, and data mining. It includes a detailed discussion on the interpretation of interval data and their use in expert systems, data bases, data warehouses, big data, and OLAP structures. The book is supported by the National Science Fund of Bulgaria under Grant No. DN-02-10. Atanassov thanks his former Ph.D. students and his daughter for their contributions. The book is structured into seven chapters, covering theoretical foundations, operations, relations, and applications of IVIFSs. The author is a professor at the Bulgarian Academy of Sciences and has made significant contributions to the theory of intuitionistic fuzzy sets and their applications in various fields.The series "Studies in Fuzziness and Soft Computing" publishes monographs and edited volumes on various topics in soft computing, including fuzzy sets, rough sets, neural networks, evolutionary computation, probabilistic and evidential reasoning, multi-valued logic, and related fields. The series is known for its rapid publication and global distribution, allowing quick dissemination of research results. The books are indexed by ISI, DBLP, Ulrichs, SCOPUS, Zentralblatt Math, GeoRef, Current Mathematical Publications, IngentaConnect, MetaPress, and SpringerLink. They are also submitted for indexing to Web of Science. The book "Interval-Valued Intuitionistic Fuzzy Sets" by Krassimir T. Atanassov explores the theory and applications of interval-valued intuitionistic fuzzy sets (IVIFSs), an extension of intuitionistic fuzzy sets (IFSs) introduced by Atanassov in 1983. IVIFSs were further developed by Georgi Gargov in 1989. The book presents Atanassov's main results and their applications, focusing on the most interesting ones. It covers various aspects of IVIFSs, including definitions, operations, relations, and operators. The book also discusses applications in areas such as fuzzy graphs, neural networks, generalized nets, and data mining. It includes a detailed discussion on the interpretation of interval data and their use in expert systems, data bases, data warehouses, big data, and OLAP structures. The book is supported by the National Science Fund of Bulgaria under Grant No. DN-02-10. Atanassov thanks his former Ph.D. students and his daughter for their contributions. The book is structured into seven chapters, covering theoretical foundations, operations, relations, and applications of IVIFSs. The author is a professor at the Bulgarian Academy of Sciences and has made significant contributions to the theory of intuitionistic fuzzy sets and their applications in various fields.