“…After that, plenty of authors have been focusing on investigating the boundedness properties of Fourier multipliers, for instance, Besov, 4 Christ et al, 5 Lu et al, 6 Tomita, 7 Yabuta, 8 Grafakos et al, [9][10][11] Chen et al, 12 Noi, 13 Yang et al, 14 and Zhao et al 15,16 Since Fourier multipliers are special cases of spectral multipliers, it is very natural to consider whether there exist some similar properties for other kinds of spectral multipliers. After the forerunner work made by Wendel,17 there appear a number of studies that focus on investigating multiplier theorems for spectral multipliers on some kinds of nilpotent Lie groups, for example, Alexopoulos, 18 Chen et al, 19 Gong and Yan, 20 Christ, 21 Christ and Müller, 22 Duong, 23 Kolomoitsev, 24 Lin, 25 Martini, 26 Mauceri and Meda, 27 Michele and Mauceri, 28 and Pini. 29 According to these studies, we introduce the original version of the Hörmander multiplier theorem for spectral multipliers on stratified groups as follows.…”