@article{MS2_1967__21_166007,
     author = {Jaak Peetre and Ioan A. Rus},
     title = {Sur la positivit\'e de la fonction de {Green.}},
     journal = {Mathematica Scandinavica},
     pages = {80--89},
     publisher = {mathdoc},
     volume = {21},
     year = {1967},
     zbl = {0164.13003},
     url = {http://geodesic.mathdoc.fr/item/MS2_1967__21_166007/}
}