Gray & Morris 1978, Theorem 9. Gray, J. D.; Morris, S. A. (April 1978). "When is a Function that Satisfies the Cauchy–Riemann Equations Analytic?". The American Mathematical Monthly. 85 (4): 246–256. doi:10.2307/2321164. JSTOR2321164.
jstor.org
Gray & Morris 1978, Theorem 9. Gray, J. D.; Morris, S. A. (April 1978). "When is a Function that Satisfies the Cauchy–Riemann Equations Analytic?". The American Mathematical Monthly. 85 (4): 246–256. doi:10.2307/2321164. JSTOR2321164.