Before revision:  Trees, as a special class of graphs, have been the focus of several papers and, recently, He and He  showed how to produce a monotone drawing of an arbitrary n-vertex tree that is contained in a 12n \times 12n grid.
After revision:  Trees, as a special class of graphs, have been the focus of several papers and, recently, He and He ~\mbox{%DIFAUXCMD mt:4 showed how to produce a monotone drawing of an arbitrary n-vertex tree that is contained in a 12n \times 12n grid.