Minimum routing cost spanning tree

In an unweighted graph, this is the spanning tree of minimum Wiener index.

[1] Hu (1974) writes that the problem of constructing these trees was proposed by Francesco Maffioli.

that depends on the approximation ratio but not on the number of vertices of the input graph, and by searching among all trees with

[5] The minimum routing cost spanning tree of an unweighted interval graph can be constructed in linear time.

[7] Several works assume that different people may have different preferences on edges in the graph, and the goal is to find a spanning tree that is "socially" best.