@article{10_1017_S0017089503001228,
     author = {EASDOWN, D. and SHNEERSON, L. M.},
     title = {PRINCIPAL {REES} {QUOTIENTS} {OF} {FREE} {INVERSE} {SEMIGROUPS}},
     journal = {Glasgow mathematical journal},
     pages = {263--267},
     year = {2003},
     volume = {45},
     number = {2},
     doi = {10.1017/S0017089503001228},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089503001228/}
}