@article{MAN_1969__182_161861,
     author = {K. RITTER},
     title = {Optimization {Theory} in {Linear} {Spaces.} {I.}},
     journal = {Mathematische Annalen},
     pages = {189--206},
     publisher = {mathdoc},
     volume = {182},
     year = {1969},
     zbl = {0177.40402},
     url = {http://geodesic.mathdoc.fr/item/MAN_1969__182_161861/}
}