  In this paper we show a Bell inequality of Clauser-Horne type for three
three-dimensional systems (qutrits). Violation of the inequality by quantum
mechanics is shown for the case in which each of the three observers measures
two non-commuting observables, defined by the so called unbiased symmetric six
port beamsplitters, on a maximally entangled state of three qutrits. The
strength of the violation of the inequality agrees with the numerical results
presented in Kaszlikowski et. al., quant-ph//0202019.
