@article{AM2_1977__15_136650,
     author = {Frank D. Farmer},
     title = {Characteristic for reflexive relations.},
     journal = {Aequationes mathematicae},
     pages = {195--200},
     year = {1977},
     volume = {15},
     zbl = {0376.55003},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__15_136650/}
}