@article{JEMS_2008_10_1_a2,
     author = {Catherine Bandle and Joachim von Below and Wolfgang Reichel},
     title = {Positivity and anti-maximum principles for elliptic operators with mixed boundary conditions},
     journal = {Journal of the European Mathematical Society},
     pages = {73--104},
     publisher = {mathdoc},
     volume = {10},
     number = {1},
     year = {2008},
     doi = {10.4171/jems/104},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/jems/104/}
}