@article{SF_1984__30_134704,
     author = {R.J. Koch},
     title = {Sandwich sets and partial order.},
     journal = {Semigroup forum},
     pages = {53--66},
     publisher = {mathdoc},
     volume = {30},
     year = {1984},
     zbl = {0528.20051},
     url = {http://geodesic.mathdoc.fr/item/SF_1984__30_134704/}
}