A blueprint for deontic logic in three (not necessarily easy) steps.

Krister Segerberg A blueprint for deontic logic in three (not necessarily easy) steps. 2007 Formal Models of Belief Change in Rational Agents http://drops.dagstuhl.de/opus/volltexte/2007/1218 conf/dagstuhl/2007P7351 db/conf/dagstuhl/P7351.html#Segerberg07