Alexander Shchitov, On Approximation of the Continuous Functions of Two Variables by the Fourier-Haar ”Angle”, IJARM Volume 5, International Journal of Advanced Research in Mathematics (Volume 5)
    The exact value of the upper bound of the approximation error by the construction of the type "angle" built using the Fourier-Haar partial sums is obtained on the function class of two variables in the uniform metric.
    Approximation, Exact Constant, Fourier-Haar ”Angle”, Fourier-Haar Sums, Fourier-Haar System, Function of Two Variables, Modulus of Continuity, Uniform Metric