@article{10_4153_CJM_1973_133_9,
     author = {Broughan, K. A.},
     title = {On the {Number} of {Structures} of {Reflexive} and {Transitive} {Relations}},
     journal = {Canadian journal of mathematics},
     pages = {1269--1273},
     year = {1973},
     volume = {25},
     number = {6},
     doi = {10.4153/CJM-1973-133-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1973-133-9/}
}