@article {MR849622,
	title = {Existence d{\textquoteright}un filtre markovien optimal en contr{\^o}le partiellement observable},
	journal = {C. R. Acad. Sci. Paris S{\'e}r. I Math.},
	volume = {303},
	number = {1},
	year = {1986},
	pages = {31{\textendash}34},
	issn = {0249-6291},
	author = {El Karoui, Nicole and Nguyen Huu Du and Jeanblanc-Picqu{\'e}, Monique}
}
