@article{MS2_1994__74_1_167280,
     author = {V.S. Sunder and Uma Krishnan},
     title = {On {Principal} {Graphs} and {Weak} {Duality.}},
     journal = {Mathematica Scandinavica},
     pages = {49--63},
     publisher = {mathdoc},
     volume = {74},
     number = {1},
     year = {1994},
     zbl = {0809.05057},
     url = {http://geodesic.mathdoc.fr/item/MS2_1994__74_1_167280/}
}