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

a collection of spanning subgraphs of $K_n$, the

complete graph on $n$ vertices.

$\cal C$ is called an Orthogonal Double Cover (ODC) if every edge of

$K_n$ belongs to exactly two elements of $\,\cal C$ and every two

elements of $\cal C$ have exactly one edge in common. Gronau, Mullin

and Schellenberg showed that the complete graph $K_n$ has an ODC

whose elements consist of cycles of length at most $4$ and an

isolated vertex, except for finitely many $n$. In this paper we

scetch the computer aided proof of the nonexistence of such an ODC

for $n=11$.