@article{CMUC_1969__10_4_a3,
     author = {Mendelsohn, E.},
     title = {An elementary characterization of the category of relational systems},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {571--588},
     publisher = {mathdoc},
     volume = {10},
     number = {4},
     year = {1969},
     mrnumber = {0268248},
     zbl = {0241.08001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1969__10_4_a3/}
}