S.K. Paikray, R.K. Jati, N.C. Sahoo, U.K. Misra, On Degree of Approximation by Product Means of Conjugate Series of a Fourier Series, BSMaSS Volume 4, The Bulletin of Society for Mathematical Services and Standards (Volume 4)
https://www.scipress.com/BSMaSS.4.5
Abstract:
    In this paper a theorem on degree of approximation of a function <i>f</i> ∈ <i>Lip</i>(<i>α</i>, <i>r</i>) by product summability (<i>E</i>, <i>q</i>)(<i>N</i>, <i>p<sub>n</sub></i>) of conjugate series of Fourier series associated with f has been established.
Keywords:
    (<i>E</i>, <i>q</i>) (<i>N</i>, <i>P<sub>n</sub></i>) Product Mean, (<i>E</i>, <i>q</i>) Mean, (<i>N</i>, <i>P<sub>n</sub></i>) Mean, Conjugate of the Fourier Series, Degree of Approximation <i>f</i> ∈ <i>Lip</i>(<i>α</i>, <i>r</i>) Class of Function, Fourier Series, Lebesgue Integral