@article {AK2001,
	title = {On optional stopping of some exponential martingales for L{\'e}vy processes with or without reflection},
	journal = {Stochastic Processes and Their Applications},
	volume = {91},
	year = {2001},
	pages = {47-55},
	author = {Asmussen, S. and Kella, O.}
}
