@article {halpern2009defining,
	title = {Defining knowledge in terms of belief: The modal logic perspective},
	journal = {The Review of Symbolic Logic},
	volume = {2},
	number = {3},
	year = {2009},
	pages = {469{\textendash}487},
	publisher = {Cambridge University Press},
	author = {Halpern, Joseph Y and Samet, Dov and Segev, Ella}
}
