@article{AM2_1968__1_135961,
     author = {Wolfgang Eichhorn and Udo M\"uller},
     title = {Regions on {Substitution,} {Curves} of {Minimal} {Cost,} and {Isoquants} of {Homogeneous} {Production} {Functions.} {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {202--203},
     publisher = {mathdoc},
     volume = {1},
     year = {1968},
     url = {http://geodesic.mathdoc.fr/item/AM2_1968__1_135961/}
}