@article{SF_1980__19_134379,
     author = {S. Bulman-Fleming and K. McDowell},
     title = {Flatness in varieties of normal bands.},
     journal = {Semigroup forum},
     pages = {139--150},
     publisher = {mathdoc},
     volume = {19},
     year = {1980},
     zbl = {0429.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__19_134379/}
}