@article{MS2_1969__25_166117,
     author = {J.A. Crenshaw},
     title = {Extreme {Positive} {Linear} {Operators.}},
     journal = {Mathematica Scandinavica},
     pages = {195--217},
     year = {1969},
     volume = {25},
     zbl = {0192.46702},
     url = {http://geodesic.mathdoc.fr/item/MS2_1969__25_166117/}
}