@article{AM2_1985__29_137100,
     author = {Tzen-Ping Liu and M.E. Thompson},
     title = {A problem arising in finite population sampling theory.},
     journal = {Aequationes mathematicae},
     pages = {307--312},
     publisher = {mathdoc},
     volume = {29},
     year = {1985},
     zbl = {0584.62010},
     url = {http://geodesic.mathdoc.fr/item/AM2_1985__29_137100/}
}