Volker Halbach Hannes Leitgeb Philip D. Welch Possible-Worlds Semantics for Modal Notions Conceived as Predicates. 179-223 2003 32 J. Philos. Log. 2 https://doi.org/10.1023/A:1023080715357 db/journals/jphil/jphil32.html#HalbachLW03