@article{10_37236_1198,
     author = {Peter J. Cameron},
     title = {Counting two-graphs related to trees},
     journal = {The electronic journal of combinatorics},
     year = {1995},
     volume = {2},
     doi = {10.37236/1198},
     zbl = {0810.05031},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1198/}
}