@article{10_4064_cm_22_1_21_24,
     author = {G. Gr\"atzer and J. P{\l}onka},
     title = {A characterization of semilattices},
     journal = {Colloquium Mathematicum},
     pages = {21--24},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1970},
     doi = {10.4064/cm-22-1-21-24},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-22-1-21-24/}
}