The erratum corrects the statement of Theorem 2 in the paper "The Internal Model Principle for Linear Multivariable Regulators" by B. A. Francis and W. M. Wonham, published in *Appl. Math. Opt.* 2 (1975), pp. 170–194. The corrected statement emphasizes that a synthesis is structurally stable at \( A_3 \) if the compensator includes an internal model of \( A_2 \) that is observable by \( u \) and controllable by \( z \) if condition (50) holds. This修正消除了解释3证明中出现的明显循环。The proofs of Theorem 2 and Proposition 3 remain unchanged. The erratum was issued by W. M. Wonham on July 8, 1976.The erratum corrects the statement of Theorem 2 in the paper "The Internal Model Principle for Linear Multivariable Regulators" by B. A. Francis and W. M. Wonham, published in *Appl. Math. Opt.* 2 (1975), pp. 170–194. The corrected statement emphasizes that a synthesis is structurally stable at \( A_3 \) if the compensator includes an internal model of \( A_2 \) that is observable by \( u \) and controllable by \( z \) if condition (50) holds. This修正消除了解释3证明中出现的明显循环。The proofs of Theorem 2 and Proposition 3 remain unchanged. The erratum was issued by W. M. Wonham on July 8, 1976.