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[[05461]] Estoppel is introduced into the Code through UCC 1-103, which states: 'Unless displaced by the particular provisions of the Uniform Commercial Code, the principles of law and equity, including the law merchant and the law relative to capacity to contract, principal and agent, estoppel, fraud, misrepresentation, duress, coercion, mistake, bankruptcy, or other validating or invalidating cause shall supplement its provisions.' [[05461]]