@article{MET_1989__36_3-4_176234,
     author = {E. von Collani},
     title = {Economically {Optimal} c- and {np-Control} {Charts.}},
     journal = {Metrika},
     pages = {215--232},
     publisher = {mathdoc},
     volume = {36},
     number = {3-4},
     year = {1989},
     zbl = {0731.62151},
     url = {http://geodesic.mathdoc.fr/item/MET_1989__36_3-4_176234/}
}