@article{10_4153_CJM_1966_085_5,
     author = {Harary, Frank and Palmer, Ed},
     title = {Enumeration of {Locally} {Restricted} {Digraphs}},
     journal = {Canadian journal of mathematics},
     pages = {853--860},
     year = {1966},
     volume = {18},
     number = {1},
     doi = {10.4153/CJM-1966-085-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1966-085-5/}
}