  We study the relationship between a notion of conjunction among conditional
events, introduced in recent papers, and the notion of Frank t-norm. By
examining different cases, in the setting of coherence, we show each time that
the conjunction coincides with a suitable Frank t-norm. In particular, the
conjunction may coincide with the Product t-norm, the Minimum t-norm, and
Lukasiewicz t-norm. We show by a counterexample, that the prevision assessments
obtained by Lukasiewicz t-norm may be not coherent. Then, we give some
conditions of coherence when using Lukasiewicz t-norm.

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