@article{BSL_2015_44_1-2_a1,
     author = {French, Rohan and Humberstone, Lloyd},
     title = {An {Observation} {Concerning} {Porte{\textquoteright}s} {Rule} in {Modal} {Logic}},
     journal = {Bulletin of the Section of Logic},
     publisher = {mathdoc},
     volume = {44},
     number = {1-2},
     year = {2015},
     url = {http://geodesic.mathdoc.fr/item/BSL_2015_44_1-2_a1/}
}