@article{SF_1974__7_134002,
     author = {L. M\'arki and O. Steinfeld},
     title = {A generalization of {Green's} relations in semigroups.},
     journal = {Semigroup forum},
     pages = {74--85},
     publisher = {mathdoc},
     volume = {7},
     year = {1974},
     zbl = {0276.20052},
     url = {http://geodesic.mathdoc.fr/item/SF_1974__7_134002/}
}