Computation of a Tree 3-Spanner on Trapezoid Graphs
  In a graph, a spanning tree is said to be a tree t-spanner of the graph if the distance between any two vertices in is at most times their distance in . The tree t-spanner has many applications in networks and distributed environments. In this paper, an algorithm is presented to find a tree -spanner on trapezoid graphs in time, where is the number of vertices of the graph. 
Sambhu Charan Barman, Sukumar Mondal and Madhumangal Pal
cs.DM