Franz Halter-Koch was professor emeritus at the University of Graz, Graz, Austria. He is the author of Ideal Systems (Marcel Dekker,1998), Quadratic Irrationals (CRC, 2013), An Invitation to Algebraic Numbers and Algebraic Functions (CRC Press, 2020), Class Field Theory and L-Functions (CRC 2022), and co-author of Non-Unique Factorizations (CRC 2006). He passed away at the end of 2023, just before finalizing this monograph. Alfred Geroldinger is professor at the University of Graz, Graz, Austria. He has published more than 100 research papers in commutative algebra and additive combinatorics. He is co-author of Non-Unique Factorizations (CRC 2006) and of Combinatorial Number Theory and Additive Group Theory (Birkhäuser 2009). Andreas Reinhart is a researcher at the University of Graz, Graz, Austria. He has published about 25 research papers in commutative algebra and algebraic number theory.