@article{MAN_1969__183_161888,
     author = {K. RITTER},
     title = {Optimization {Theory} in {Linear} {Spaces.} {Part} {II.} {On} {Systems} of {Linear} {Operator} {Inequalities} in {Partially} {Ordered} {Normed} {Linear} {Spaces.}},
     journal = {Mathematische Annalen},
     pages = {169--180},
     publisher = {mathdoc},
     volume = {183},
     year = {1969},
     zbl = {0186.18202},
     url = {http://geodesic.mathdoc.fr/item/MAN_1969__183_161888/}
}