**MSC:**- 05B30 Other designs, configurations, See also {51E30}
- 05B15 Orthogonal arrays, Latin squares, Room squares

orthogonal double cover (ODC) of K_n if every edge of K_n belongs to

exactly two members of P, and if every two members of P share exactly

one edge. P is an ODC of K_n by some graph G if all graphs in P are

isomorphic to G. Gronau, Mullin, and Rosa conjecture, that every tree

except the path with 4 vertices admits ODC of the fitting K_n. They

proved, this to be true for trees of diameter 3. In this paper, we

show the correctness of their conjecture for some classes of trees

of diameter 4.