A proof of the great Picard theorem (Q1772525)

Great Picard Theorem: If \(z_0\) is a point of the Riemann sphere \(\mathbb C^*\) and \(f\) is a function which is holomorphic in a punctured neighborhood of \(z_0\) and has an essential singularity at \(z_0\) then in every neighborhood of \(z_0\) the function \(f\) takes every complex value, with at most one exception, infinitely many times. The author gives a simple and self contained proof of the Great Picard Theorem based on certain Harnack-type inequalities due to J. Lewis.