  In this paper a finite discrete time market with an arbitrary state space and
bid-ask spreads is considered. The notion of an equivalent bid-ask martingale
measure (EBAMM) is introduced and the fundamental theorem of asset pricing is
proved using (EBAMM) as an equivalent condition for no-arbitrage. The
Cox-Ross-Rubinstein model with bid-ask spreads is presented as an application
of our results.
