@article{SF_1979__18_134346,
     author = {M. Satyanarayana and C.S. Nagore},
     title = {On naturally ordered semigroups.},
     journal = {Semigroup forum},
     pages = {95--104},
     publisher = {mathdoc},
     volume = {18},
     year = {1979},
     zbl = {0425.06010},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__18_134346/}
}