Soon-Mo Jung was a mathematics professor at Hongik University in Republic of Korea from March 1995 to February 2023. His research interests include measure theory, number theory, Euclidean geometry, and classical analysis. He received his bachelor's, master's and doctoral degrees in 1988, 1992 and 1994, respectively, from the Department of Mathematics at the University of Stuttgart, Germany. In particular, among his important research topics, classical analysis and Euclidean geometry account for a large portion, and these topics are closely related to the Aleksandrov-Rassias problems, the main subject of this book. He published numerous papers and books in the fields of measure theory, fractal geometry, number theory, classical analysis, Euclidean geometry, discrete mathematics, differential equations, and functional equations.