Dr. B. V. Senthil Kumar works at the Department of Information Technology, Nizwa College of Technology, Nizwa, Oman. His areas of interest include the solution and stability of functional, differential and difference equations, operations research, statistics and discrete mathematical structures. Having obtained his Ph.D. in 2015, he has more than 20 years of teaching and 10 years of research experience. He has published more than 50 research papers in respected national and international journals; co-authored three books; and contributed three book chapters. In addition, he is a member of various mathematical societies and serves as a reviewer or editorial committee member for several journals.Dr. Hemen Dutta is a regular faculty member at the Department of Mathematics, Gauhati University, India. His research interests include mathematical analysis, mathematical modeling, etc. He has published over 100 research papers and book chapters, as well as 14books, including textbooks, reference books, monographs, edited books and conference proceedings. He has also published several articles in newspapers, magazines and science portals.

• Introduction to Functional equations and Ulam stability theory.- Stability and instability of multiplicative inverse type tredecic and quottuordecic functional equations in non-Archimedean spaces.- Estimation of inexact multiplicative inverse type quindecic and sexdecic functional equations in Felbin’s type fuzzy normed spaces.- Classical approximations of multiplicative inverse type septendecic and octadecic functional equations in quasi-β-normed spaces.- Ulam stabilities of multiplicative inverse type novemdecic and vigintic functional equations in intuitionistic fuzzy normed spaces.- Solution to the Ulam stability problem of multiplicative inverse type unvigintic and duovigintic functional equations in paranormed spaces.- Inexact solution of multiplicative inverse type trevigintic and quottuorvigintic functional equations in matrix normed spaces.