@article{SF_1972__4_133904,
     author = {M. Petrich},
     title = {A simple construction of semigroups all of whose subsemigroups are left ideals.},
     journal = {Semigroup forum},
     pages = {262--266},
     publisher = {mathdoc},
     volume = {4},
     year = {1972},
     zbl = {0261.20053},
     url = {http://geodesic.mathdoc.fr/item/SF_1972__4_133904/}
}