Comment:
Other problems which aim at finding spanning trees that maximize a
single objective function have been considered. In particular, the
problems of finding a spanning tree that has maximum diameter, or
maximum height with respect to a specified root are not in APX, the
problems of finding a spanning tree that has maximum sum of the
distances between all pairs of vertices, or maximum sum of the
distances from a specified root, are not in PTAS [180].
The problem of finding a spanning tree that maximizes the number of paths
that connect pairs of vertices and pass through a common arc is
approximable within 1.072 [110].
.