@article{GDZPPN00247221X,
title = {Maximum Principles and Duality.},
journal = {Monatshefte f\"ur Mathematik},
volume = {62},
year = {1958},
pages = {56-75},
zbl = {0094.29901},
url = {http://dml.mathdoc.fr/item/GDZPPN00247221X}
}
Redheffer, Raymond M. Maximum Principles and Duality.. Monatshefte für Mathematik, Tome 62 (1958) pp. 56-75. http://gdmltest.u-ga.fr/item/GDZPPN00247221X/