@article{10_4153_CMB_1971_094_3,
     author = {Nelson, Evelyn},
     title = {The {Lattice} of {Equational} {Classes} of {Semigroups} with {Zero}},
     journal = {Canadian mathematical bulletin},
     pages = {531--534},
     year = {1971},
     volume = {14},
     number = {4},
     doi = {10.4153/CMB-1971-094-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1971-094-3/}
}