I can suggest the type of high-quality research articles you should look for and where you might find them:
"Advanced Studies in Type-2 Fuzzy Sets and Systems" by Jerry M. Mendel. This is an academic paper or potentially a book chapter that would typically delve into the mathematical details of type-2 fuzzy sets. Jerry M. Mendel is a prominent figure in the study of fuzzy systems, and his work often encompasses step-by-step explanations of the underlying mathematical principles.
"Operations on Type-2 Fuzzy Sets" by Robert John, Simon Coupland, or similar researchers in the field of fuzzy logic. A paper of this nature would provide concrete computational procedures, detailed explanations of the operations on type-2 fuzzy sets, and their practical applications.
Research articles published in journals such as "IEEE Transactions on Fuzzy Systems" or "Information Sciences" that focus on fuzzy set theory. These journals often contain articles that include rigorous mathematical analyses of operation on fuzzy sets and discuss practical applications ranging from engineering to decision-making processes.
For detailed and authoritative information, you could consult SpringerLink, IEEE Xplore, ScienceDirect, or Google Scholar databases using search terms such as "type 2 fuzzy sets operations" or "mathematical operations on type 2 fuzzy sets" to find relevant scholarly articles.